A controller of an oil pressure control system for an automatic transmission, the system including: a manual valve having a sleeve and a spool and changing an oil passage to the automatic transmission; a detent lever having engagement grooves and positioning the spool; an engagement member including an engagement unit for the grooves and a bias unit biasing the engagement unit; and a motor rotating the detent lever, comprises: a shift range detecting unit; a range switch determining unit determining whether the shift range is switched; a temperature detecting unit; a temperature determining unit determining whether environmental temperature is lower than a predetermined temperature; and a power controlling unit supplying, to the motor, power for setting a maximum value of a rotary torque of rotating the detent lever to be a predetermined value when the shift range is switched and the environmental temperature is lower than the predetermined temperature.