Shift controller of automatic transmission and shift control method of automatic transmission

In order to satisfy both enhancement of fuel economy and limitation on frequent shift operation more surely, the shift controller (1) of an automatic transmission (20) is provided with a shift state judgment section (65) for judging whether a judgment of shift is available or not for the automatic transmission (20), a shift time estimation section (67) for estimating, if available, a completion time of shift, i.e. a time required for shifting from a current shift stage (g0) to another shift stage (g1) and then further shifting to the current shift stage (g0), a fuel consumption estimation section (69) for estimating a first fuel consumption (F1) required when running in the current shift stage (g0) for the completion time of shift and a second fuel consumption (F2) required when shifting from the current shift stage (g0) to another shift stage (g1) and then further shifting to the current shift stage (g0), and a fuel consumption judgment section (70) for judging the effectiveness of shifting based on the first fuel consumption (F1) and the second fuel consumption (F2), wherein a shift control section (72) alters such a judgment that shifting is to be made to another shift stage (g1) at the time of the judgment of shift according to judgment results from the fuel consumption judgment section (70).