A method of estimation of the collision frequency in the lower ionosphere using the field intensity of a ground based LF signal observed by a rocket is described. The magnetic intensity profiles, in the ionosphere, of a ground based signal observed by a rocket and the electron density simultaneously observed at several altitudes are analyzed by iterative calculations based on a simple WKB solution. The collision frequency for mono-energetic electrons, vm, in the upper D and E regions was actually estimated from the altitude profile of the right handed circularly polarized component of a 40kHz ground based signal observed by means of theK-9M-53 rocket. As a result, the following relationships were obtained; Vm=4.8x105P for the upper D region and vm=11.0x105P for the E region, where P(Newton/m2) was taken from CIRA (1972).