To provide an automatic gear shift controller capable of quickly shifting down a gear in a transmission when a driver shows a desire to accelerate, in the automatic gear shift controller for automatically shifting the gear to a gear stage capable of achieving the traveling of the lowest fuel consumption within a range free from the stall of a vehicle.

A gear shift control means is mounted for determining a fuel consumption rate SFC and the minimum torque requirement to keep a present driving stage by every gear stage of the transmission 3, selecting the gear stage of the lowest fuel consumption rate SFC among the gear stages of which the torque requirement is less than the maximum torque of an engine, and shifting the gear of the transmission 3 to the target gear stage. The gear shift control means selects the gear stage at a lowest speed side among the plurality of gear stages, as the target gear stage, when the plurality of gear stages of the lowest fuel consumption rate exist in the gear stages of which the torque requirement is less than the maximum torque, and an accelerator opening ACC and/or the change of accelerator opening ΔACC in a specific period are more than specific values.