When the protruding length of a cutting blade 11 protruding below a lower surface of a base 2 of a portable machining device 1 is set to its maximum length, at least a part of a controller 31 for controlling an electric motor 12 is configured to be located behind a handle 14 in the front-to-rear direction. Furthermore, the controller 31 is disposed so as to be tilted in the left-to-right direction or in the up-to-down direction with respect to the cutting blade 11. Because of this configuration, the height of the handle 14 can be restricted and at the same time the controller 31 can be disposed in a compact manner.