Since the progress in the fabrication techniques of thin-films of exotic materials such as strongly correlated heavy-fermion compounds, microscopic studies of the magnetic and electronic properties inside the films have been needed. Herein, we report the first observation of 115 In nuclear quadrupole resonance (NQR) in an epitaxial film of the heavy-fermion superconductor CeCoIn5, for which the microscopic field gradient within the unit cell as well as magnetic and superconducting properties at zero field are evaluated. We find that the nuclear spin-lattice relaxation rate in the film is in excellent agreement with that of bulk crystals, whereas the NQR spectra show noticeable shifts and significant broadening indicating a change in the electric-field distribution inside the film. The analysis implies a displacement of In layers in the film, which however does not affect the magnetic fluctuations and superconducting pairing. This implies that inhomogeneity of the electronic field gradient in the film sample causes no pair breaking effect.Recently developed thin-film fabrication techniques, such as molecular beam epitaxy (MBE) and pulsed laser deposition, can be used to fabricate films consisting of not only simple substances but also multi-element materials. In thin-films, it is expected that the electronic states can be manipulated by effects that are difficult to achieve in bulk systems, such as two-dimensionality [1][2][3][4], surface states [5, 6], and proximity effects between the sample and the substrate [7]. Recently, epitaxial thin film and superlattice samples of heavy-fermion (HF) CeM In 5 (M = Co, Rh) have been fabricated. The superlattices consisting of CeM In 5 / normal-metal YbM In 5 have attracted interest for their anomalous features such as enhancement of the anisotropy of the superconducting (SC) upper critical field (H c2 ) [8][9][10] Although such attractive phenomena have been reported, unfortunately the experimental techniques to study the physical properties of film samples are quite limited. For example, neutron scattering experiments, which clarify magnetic properties decisively, usually require a huge volume of the sample, typically around the order of 1 cm 3 . Specific-heat and thermal-conductivity measurements, which are powerful tools to determine the SC gap structure, are also difficult since the huge contribution from the substrate masks the small contribution arising from the film sample.Nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) are quite suitable measurements for film samples, if the material includes the NMR/NQR possible nuclei, because the measurements can detect the electronic state in only the film. In NMR/NQR experiments, the small sample volume reduces the signal intensity but the large surface area partially compensates the loss of signal intensity because NMR/NQR measurements mainly detect the surface region with several microns of depth. In addition, the experiments are able to select interesting block layers of the superlattice samples and ...