A variable compression ratio internal combustion engine is equipped with a variable compression ratio mechanism configured to change an engine compression ratio in accordance with a rotational position of a control shaft, and a housing that accommodates therein a drive motor for changing and holding the rotational position of the control shaft. A reference position of the control shaft is learned in a state where a position of maximum rotation of the control shaft in a first rotational direction has been mechanically restricted by bringing a first movable part, which operates in conjunction with the control shaft, into abutted-engagement with a first stopper provided outside of an engine body. Subsequently, a maximum conversion angle range of the control shaft is learned in a state where a position of maximum rotation of the control shaft in a second rotational direction has been mechanically restricted by a second stopper.