An electric cutting tool including a housing (1) and a motor (2). The motor (2) is removably mounted in a cavity arranged at the back end of the housing (2), and the outer diameter of the motor (2) is matched with the diameter of the cavity. A turnover opening back cover (3) is hinged at the opening at the back end of the cavity. The back cover (3) is locked with the housing (1) by means of a locking structure arranged on its side, and presses against the back end of the motor (2) after closing. A pair of electrode posts (21) are provided at the front end of the motor (2), and a pair of electrode sockets (18) corresponding one-to-one with the pair of electrode posts (21) are provided in the bottom surface of the cavity. A circumferential stop structure is provided between the radial outer surface of the motor (2) and the inner wall of the cavity. The motor (2) is circumferentially fastened by the circumferential stop structure, causing the polarities of the electrode posts (21) and those of the electrode sockets (18) matching.