A shift control device for an automatic transmission is provided with an automatic shift mode and a manual shift mode instructed by a manual operation of a driver. The shift control device includes at least one processor and at least one memory including computer program code that cause the shift control device to measure a following distance between an own vehicle and a front vehicle, measure an accelerator opening of an engine, judge whether the measured following distance is equal to or less than a predetermined set value if a downshift is instructed by a manual operation of the driver and the measured accelerator opening is fully closed, and determine a target shift stage based on the following distance if the following distance is equal to or less than the set value. Accordingly, the shift control device downshifts to the target shift stage.