A hose clamp has a clamp body, operation pieces, an engaging claw, a receiving portion, an arch shaped opening and a slide guide portion. The clamp body is composed of a plate spring member bent into a ring shape. The operation piece has two legs at one end of the clamp body, and has an operation portion at ends of the legs. The operation piece has a leg at the other end of the clamp body, and has an operation portion at an end portion of the leg. The receiving portion is formed on the operation portion and can engage with the engaging claw. The arch shaped opening is formed on the operation portion, and allows the engaging claw to pass therethrough. The engaging claw and the slide guide portion are disposed on one side of the leg of the operation piece. The slide guide portion contacts with the leg in order to make the engaging claw be opposed to the arch shaped opening.