To provide a foldable cutting knife capable of simply performing a taking in and out operation of the blade body in using and storing the cutting knife with one hand and fingers and stably performing cutting operation by holding the grip and the blade body in using in the folding cutting knife.

The foldable cutting knife 1 has the blade body 50 foldably and storably pivotably supported on the grip shank 10. A locking piece 51 is formed on the blade body 50 at the base end side rather than a pivotal support part 40, a receiving groove 20 for receiving the locking piece 51 is formed on the grip shank 10, and a locking guide edge 21 for slide guiding to lock is provided on the receiving groove 20 while elastically deforming the locking piece 51.