To provide a speed change gear capable of detecting failures of valves forming a hydraulic control circuit using a hydraulic pressure of an oil discharged from an oil pump driven by an engine.

A hydraulic control circuit 40 supplies an oil supplied from a first oil pump OP1 to a cooling oil passage L1, a lubrication oil passage L2, and a clutch oil passage L3. The hydraulic control circuit 40 includes: a regulator valve 61; two solenoid valves 62, 63; two shift valves 64, 65; and a relief valve 66. The state of the regulator valve 61 is switched by a solenoid 62a and the states of the second shift valve 65 and the relief valve 66 are switched by a solenoid 63a. Oil temperature sensors 44, 47, 53 are respectively provided at an electric motor 11, the clutch oil passage L3, and an oil pan 51. An ECU 50 detects failures of the valves 61 to 66 on the basis of output values of the sensors 43, 47, 53.