A phase-to-phase insulation partial discharge inspection apparatus includes: an impulse power supply (1) configured to apply an impulse voltage having a voltage rise time period tr which satisfies an expression “tr>(τcoil·Vmax)/(PDIV)” to a rotary electric machine (2); a measurement section (12) configured to measure partial discharge which occurs when the impulse voltage is applied to the rotary electric machine (2); and a decision section (15) configured to determine that, when partial discharge is not measured by the measurement section (12), a phase-to-phase insulation performance is acceptable. In the expression, τcoil is a surge propagation time period of one coil of a rotary electric machine winding, PDIV a partial discharge inception voltage between winding turns, and Vmax a peak of a partial discharge testing voltage for the phase-to-phase insulation.