To provide a method for determining model of electric actuator adapted to be capable of automatically determining a model of electric actuator driven by reducing rotations of a stepping actuator by a reduction gear mechanism provided with a encoder reduction.

A method for determining a model of electric actuator comprises the steps of measuring B-H characteristics of flux density and magnetic field by applying a predetermined voltage on a coil of a stepping motor and detecting an electric current that flows therethrough at this moment and an induced electromotive force; determining a B-H characteristics pattern of the stepping motor by comparing this with a B-H characteristics reference pattern; as well as measuring a reduction ratio by the reduction gear mechanism by counting pulses from an encoder during a predetermined rotation of the stepping motor, and comparing these B-H characteristics pattern and reduction ratio with a model table in which models of electric actuators have been classified in advance taking the both data as parameters, thereby determining a model of electric actuator in question.