The invention relates to an oil leakage inspection device for a high-voltage circuit of a circuit breaker with a hydraulic mechanism. The oil leakage inspection device comprises a box type body, one sidewall of the body is provided with an oil level gauge for measuring an oil level, and the sidewall of the body is also provided with an observation window for observation of conditions inside the body; the bottom of the body is connected with an oil valve for oil injection and discharge through an oil pipe; the top part of the body is provided with a removable top cover which can be opened for arrangement of the hydraulic mechanism of the circuit breaker; the observation window is arranged on a sidewall adjacent to or opposite to the sidewall with the oil level gauge and is fixed on the sidewall by a rubber pad and a cover plate through bolts in a sealing way; and the bottom of the body is provided with a support seat made of a stainless steel plate, and four bottom corners of the body are provided with fixing bolt holes. Normal pressurization of an oil pump is simulated. After pressurization is completed, leakage inspection can be performed for every sealed valve port. Therefore, leakage inspection can be performed for every sealed valve port after pressurization in case of oil leakage of the high-voltage circuit of an FX22 switch, and observation can be performed in a closed position after treatment.