Abstract: A controller for an automatic transmission includes a sensor for detecting a vehicle operating condition, a transmission for changing a rotational ratio of drive and driven shaft, and an ordering mechanism for ordering shift change to drive the transmission based on the operating condition detected by the sensor. Also provided are a cornering mechanism for detecting vehicle cornering, an accelerating detection mechanism for detecting vehicle acceleration, and an inhibiting mechanism for inhibiting shift down to lower the rotational ratio of drive and driven shaft in the transmission by the controller in case both vehicle cornering detected by the cornering mechanism and vehicle acceleration detected by the accelerating detection mechanism are equal to or greater than the first and second preset values, respectively.