To provide a knife having spare blade with which structure and operations are simplified.

A knife 10 has a grip 12, which is composed of a main body 13 and a lid 14 movable in longitudinal direction (x) in respect to this main body, and a spare blade 11 and the lid 14 can be moved from an opening position to a closing position. At the opening position, a front pressing plane 20 on the lid 14 can be pressed inside toward the blade 11 against a spring return operation. At the closing position, the lid 14 pushes a supporter 17 outside through the spring return operation while using a holding plane 30 engaged with the supporter 17 at the main body 13. At the closing position, the lid 14 is stricted by friction coupling, fitting engagement or insertion coupling between a rear end range 22 of the lid 14 and a rear supporting stand 18 at the main body 13.