A method for detecting rotation direction of an AC motor, when supplying a three-phase AC electric power to said AC motor, after stoppage of an output thereof, in an electric power conversion device, comprising a smoothing capacitor for smoothing an electric power to be supplied from an electric power source, and an inverter for inverting a DC electric power from said smoothing capacitor into a three-phase AC electric power having a desired frequency thereof, thereby supplying said inverted AC electric power having the desired frequency to said AC motor, comprising the following steps of: detecting a timing when AC voltages of two phases selected from three-phase AC inductive electric power from said AC motor intersect with each other; forming a flow path for freewheeling current only between said inverter and said AC motor, with the inductive electric power of said AC motor, by driving part of switching elements building up said inverter, selectively, at that timing detected, by: turning the switching elements ON, selectively, corresponding to said two phases selected, while turning the switching element corresponding to the other one phase OFF, from the switching elements of three phases building up said upper-side arm and said lower-side arm, when driving said inverter at that timing; or turning the switching elements OFF, selectively, corresponding to said two phases selected, while turning the switching element corresponding to the other one phase ON, from the switching elements of three phases building up said upper-side arm and said lower-side arm, when driving said inverter at that timing; detecting the freewheeling current flowing through said flow path formed; and thereafter determining the rotation direction after stoppage of the output of said electric power conversion device, depending on that freewheeling current detected; wherein the rotation direction after stoppage of the output of said electric power conversion device is determined depending on amplitude of the freewheeling current detected at that timing and wherein the switching elements of an upper-side arm or a lower-side arm building up said inverter are driven, selectively, when driving said inverter at that timing. detecting a timing when AC voltages of two phases selected from three-phase AC inductive electric power from said AC motor intersect with each other; forming a flow path for freewheeling current only between said inverter and said AC motor, with the inductive electric power of said AC motor, by driving part of switching elements building up said inverter, selectively, at that timing detected, by: turning the switching elements ON, selectively, corresponding to said two phases selected, while turning the switching element corresponding to the other one phase OFF, from the switching elements of three phases building up said upper-side arm and said lower-side arm, when driving said inverter at that timing; or turning the switching elements OFF, selectively, corresponding to said two phases selected, while turning the switching element corresponding to the other one phase ON, from the switching elements of three phases building up said upper-side arm and said lower-side arm, when driving said inverter at that timing; turning the switching elements ON, selectively, corresponding to said two phases selected, while turning the switching element corresponding to the other one phase OFF, from the switching elements of three phases building up said upper-side arm and said lower-side arm, when driving said inverter at that timing; or turning the switching elements OFF, selectively, corresponding to said two phases selected, while turning the switching element corresponding to the other one phase ON, from the switching elements of three phases building up said upper-side arm and said lower-side arm, when driving said inverter at that timing; detecting the freewheeling current flowing through said flow path formed; and thereafter determining the rotation direction after stoppage of the output of said electric power conversion device, depending on that freewheeling current detected; wherein the rotation direction after stoppage of the output of said electric power conversion device is determined depending on amplitude of the freewheeling current detected at that timing and wherein the switching elements of an upper-side arm or a lower-side arm building up said inverter are driven, selectively, when driving said inverter at that timing.