A cooling structure of an oil cooling motor may include a housing, a front cover and a rear cover each mounted at both sides of a housing along a length direction of the housing, a rotor shaft extending through the housing and have both ends rotatably supported by bearings of the front cover and the rear cover, a rotor disposed in the housing and rotatably supported by the rotor shaft, a front oil supply groove and a rear oil supply groove formed on opposing inner sides of the front cover and the rear cover and configured to temporarily store oil stored in a bottom of the housing and scattered by churning of the rotor, and a front cover passage and a rear cover passage configured to communicate with the front oil supply groove and the rear oil supply groove, respectively.