To provide such an automatic transmission controller for a vehicle as being capable of prohibiting shift-up from the second variable speed gear to the third variable speed gear when driving wheels are slipped and accurately cancelling the prohibiting of shift-up.

When a throttle opening TH is increased by stepping an accel pedal when a vehicle is started on an ice-covered road with a low road surface friction coefficient, a body speed V detected in accordance with the rotating number of the output shaft of an automatic transmission is abruptly increased with the occurrence of slip but an actual body speed V(F) is gently increased because grip between a driving wheel and a road surface is lost. Body acceleration which is normally generated on a flat road is previously stored, an estimated body speed VYS is calculated from the body acceleration and a time passed after the slip occurs and the grip between the driving wheel and the road surface is judged to be recovered when the detected body speed V is below the estimated body speed VYS, so that the prohibition of shift-up is cancelled.