A cutter includes a replaceable blade detachably attached to a cutter body. A main body block of the cutter body includes a container section that houses a slide block, a main body supporting section, and a main body connecting section that connects with the replaceable blade. The slide block includes a rear-side supporting section, a slide connecting section, a flexible section, and a wing section. A front side retaining section that retains the wing section from a front side is formed in at least one side of the container section in a height direction, and the front side retaining section includes a protruding engaging section. In an attached state, the wing section is engaged from a foreside by the protruding engaging section, and the wing section is released from the protruding engaging section by bending the flexible section of the slide block from the attached state.