A hydraulic circuit (50) for a power transmission system including a CVT comprises an oil pump (24) driven by an engine, a regulator valve (51) capable of regulating the pressure of the working fluid from the oil pump (24) and supplying said fluid to a primary cylinder (47), a linear solenoid valve (SLS) that supplies the regulated working fluid from the oil pump (24) to a clutch (C1) of a switching mechanism for changing the drive mode to forward or backward drive, an electromagnetic pump (70) for supplying the working fluid to the clutch (C1) and a switching valve (60) capable of switching the hydraulic circuit to supply the working fluid from the linear solenoid valve (SLS) to the clutch (C1) when working fluid from the oil pump (24) is being discharged or to supply the working fluid from the electromagnetic pump (70) to the clutch (C1) when the working fluid from the oil pump (24); is not being discharged.