To provide a clamp 1 for fixing a flexible tube that fixes a flexible tube 3 to the outer wall W and facilitate wiring work of cables such as electrical wiring and communication wiring which are inserted into the flexible tube 3, and can waterproof the flexible tube 3 simply and certainly.

The clamp 1 for fixing the flexible tube includes a flange 4 of tubular shape which is contained in a through-hole H while abutting on one side surface W1 of the outer wall W at the circumference of the through-hole H and which allows a flexible tube 3 to be inserted, an outer fitting member 5 having a click 12 which engages with the bellows shape 31 of an inserted flexible tube 3 and regulates sliding of the flexible tube 3 in one direction, a tubular bolt member 7 having a male screw 13 formed on the outer circumferential surface and screwed into a female screw 6 in the inner circumferential surface on one end side of the outer fitting member 5 and which allows the flexible tube 3 to be inserted, and a nut member 8 which is screwed into the male screw 13 of the tubular bolt member 7 and abuts on the other side surface W2 of the outer wall W.