A control device for controlling a continuously variable transmission (5) is disclosed. The control device has an oil pressure control unit (100) which supplies an oil pressure to a primary pulley (10) and secondary pulley (11) based on a command signal indicative of a target speed-reduction ratio, a sensor (26) which detects a rotation speed ( Np1 ) of the primary pulley (26), and a controller (20) which transmits the command signal indicative of the target speed-reduction ratio to the oil pressure control unit (100). The controller is programmed to set the target speed-reduction ratio to a first speed-reduction ratio ( R1 ); calculate a first predetermined rotation speed ( N1 ) of the primary pulley at which the V-belt reaches a first limiting temperature ( T1 ) at the first speed-reduction ratio ( R1 ); calculate a first elapsed time after the detected rotation speed ( Np1 ) of the primary pulley exceeds the first predetermined rotation speed ( N1 ); maintain the first speed-reduction ratio ( R1 ) when the first elapsed time is equal to or less than a first predetermined time; and set the target speed-reduction ratio to a second speed-reduction ratio ( R2 ) smaller than the first speed-reduction ratio ( R1 ) when the first elapsed time exceeds the first predetermined time. At the second speed-reduction ratio ( R2 ), the temperature of the V-belt should become equal to or less than the first limiting temperature ( T1 ) throughout the permitted rotation speed region of the primary pulley. Thus, starting acceleration performance of the continuously variable transmission is enhanced.