The invention relates to a coating machine, in particular to a coating machine with a replaceable drum. The coating machine with the replaceable drum solves the problem that an existing coating machine can only coat materials with the volume or weight changing within a certain range, and cannot adapt to production when the volume or weight of materials is large in change. Two parallel first guide rails are arranged inside a machine body of the coating machine in the front-back direction, a drum unit is detachably installed in a front door of the machine body, the drum is detachably and rotationally installed on a drum supporting cart, a transmission shaft extending forwards is installed on the rear portion in the machine body and located above the first guide rails, the rear end of the drum is provided with a shaft sleeve extending backwards along the axis of the drum, the shaft sleeve is matched with the transmission shaft, and the distance between the axis of the transmission shaft and the first guide rails corresponds to the distance between the axis of the shaft sleeve and the bottom faces of a plurality of guide wheels. The coating machine is applied to the coating procedure in the pharmaceutical, food and chemical fields.