A shift controller includes: a shift control unit automatically shifting gears of an automatic transmission using a basic shift line map; a shift line map switching control unit switching from the basic shift line map to a high fluid temperature shift line map set on a lower vehicle speed side when a hydraulic fluid temperature in the automatic transmission is higher than a predetermined value; and a low power state determination unit determining whether a vehicle is in a low power state in which a required power related value used for gear shift determination is lower than a predetermined determination value. The shift line map switching control unit switches from the high fluid temperature shift line map back to the basic shift line map when the hydraulic fluid temperature is lower than the predetermined value and the vehicle is in the low power state.