The present invention provides a control unit. When the control unit performs shifting from a state in which a first shift speed is established by supplying engagement pressures to both hydraulic oil chambers and engaging a predetermined engagement element to a second shift speed by switching engagement and disengagement states of engagement elements other than the predetermined engagement element (Step S1), the control unit reduces the supply of the engagement pressure to one of the two hydraulic oil chambers to a level lower than that in the state in which the first shift speed is established (Step S3).