We calculate the thermal partition function of DLCQ superstring on the maximally supersymmetric pp-wave background, which is realized as the Penrose limit of orbifolded AdS 5 × S 5 and known to be dual to the N = 2 "large" quiver gauge theory as shown by S. Mukhi, M. Rangamani and E. Verlinde, hep-th/0204147. Making use of the pathintegral technique, we derive the manifestly modular invariant expression and show the equivalence with the free energy of second quantized free superstring on this background.The "virtual strings" wound around the temporal circle play essential roles for realizing the modular invariance and for a simple analysis on the Hagedorn temperature. We also