A hydraulic circuit for a transmission, according to the present invention, comprises a regulator valve (31), a plurality of control valves (34, 35, 45), a restrictor (41), a bypass oil passage (61), a bypass closing valve (42), and a signal pressure generating valve (48). The regulator valve regulates oil discharged from a hydraulic pump driven by a motor to produce line pressure. The plurality of control valves control an operation of the transmission using the line pressure. The control valves include at least one electric control valve. The restrictor is formed on a discharge oil passage which is connected to the regulator valve. The bypass oil passage connects the upstream side and the downstream side of the restrictor while bypassing the restrictor. The bypass closing valve is closable the bypass oil passage by receiving oil pressure produced when the electric control valve breaks down. The signal pressure generating valve generates a signal pressure which corresponds to one of oil pressure on the upstream side of the restrictor and an oil pressure difference between the upstream side and the downstream side when the bypass oil passage is closed. Accordingly, the regulation of line pressure by a regulator valve is not influenced for generating signal pressure corresponding to the speed of the motor and controlling oil pressure when failure occurs.