NOVELTY - The electric leak detecting apparatus finds the phase difference between an AC signal voltage and an AC current of a detecting signal, detects the resistance component by computing the real part of an admittance using the phase difference, and compares the resistance component with a threshold value.    USE - For detecting an electric leak caused by deteriorated insulation between vehicle body and battery pack in an electric motorcar having a high voltage battery pack insulated from the vehicle body electrically to prevent electrical shocks.    ADVANTAGE - Avoids error due to the floating capacity and errors of the electric leak resistance of the battery pack itself. Avoid problem where the detection side and driving side are connected with a DC on account of the detection.    DETAILED DESCRIPTION - The electric leak detecting apparatus has a source for generating an AC signal, which supplies a sine wave detecting signal S1 of a single frequency (f1) Hz to between vehicle body and a low potential side or a high potential side of a battery pack; a condenser having capacitance (Cd) for insulating the AC source from the low potential side or high potential side of the battery pack with respect to direct currents and for connecting the AC source to low or high potential side of battery pack with respect to alternating currents; a voltage detecting circuit for detecting an AC signal voltage of detecting signal S1 at either side of the condenser; a current detecting circuit for detecting an AC signal current i of detecting signal S1; an admittance detecting circuit for computing an electric leak admittance (Y) from the AC signal voltage and AC signal current i of the detecting signal S1; a phase discriminating circuit for finding a phase difference f between the AC signal voltage and AC signal current i of the detecting signal S1; a resistance component detector for detecting a resistance component by computing a real part of admittance (Y) from admittance (Y) and phase difference f; and a comparator for comparing the resistance component with a threshold value.    DESCRIPTION OF DRAWING(S) - The drawing shows a diagram to illustrate the electric leak detecting apparatus.