A rotary cutter includes a housing, a swing member rotatably attached to the housing and having a trigger extended out of the housing and having a curved slot and an enlarged opening communicating with each other. A button is slidably engaged through the housing, and includes a reduced stud to engage into the curved slot of the swing member, and a latch having an outer diameter to prevent the latch from engaging into the curved slot of the swing member. A link is coupled to the swing member, and includes a pole slidably engaged in the curved channel of the housing, and a rotary cutter blade is secured to the link with a shaft, to allow the cutter blade to be moved into and out of the working end portion of the housing by the link and the swing member.