Heating power control is performed in thermally assisted magnetic recording using a patterned recording medium. Trial writing is performed by continuously changing a heating power intensity with respect to a pattern row of a trial writing area provided in plurality on the recording medium. From a reproduction signal thereof, a minimum heating power of recording that is a boundary power between recording and non-recording, and a maximum heating power of recording that is a boundary power between recording and a heating power by which recorded information of an adjacent pattern is deleted are determined to decide an optimum recording power.