Abstract: A structure for mounting a motor of a planing machine includes a hollow base, an axle casing fitted in said base and provided with a spindle for connecting with a planing cutter, a first pulley arranged under said spindle so that a belt connects said first pulley with a second pulley of a motor, wherein said axle casing is provided at a bottom with an extension having a circular hole and a curved groove subtending the center of the circular hole, a motor cover is installed on one end of a motor and has a pair of lugs in which is fitted an end of said extension, a pin is inserted into said lugs and said circular hole to form a pivot therebetween, and a locking handle is threadedly engaged with one of said lugs so that said motor is fastened on one side of said axle casing.