A medical tube clamp comprising: a first plate part and a second plate part connected at a curved portion; compressive protrusions (22, 24) provided on opposing surfaces of the first plate part and the second plate part that close a medical tube by compression between them; and a locking means that elastically deforms the curved portion and retains the medical tube in a closed state by locking the first and second plate parts (14, 16) at a location close to each other, at least one of the first plate part and the second plate part has a pair of side walls on both sides that protrude out toward another of the first plate part and the second plate part, in order to prevent the medical tube from being displaced off sideways, the other of the first plate part and the second plate part has a central guide protrusion that protrudes out toward the one of the first plate part and the second plate part, the medical tube clamp being characterized in that both sides of a tip portion of the central guide protrusion protrude out toward a center to make sloping guide surfaces that guide the central guide protrusion into a gap between the pair of side walls while preventing interference against the pair of side walls during a relative displacement of the first and second plate parts (14, 16) in a direction of bringing them closer to each other, and an engagement prevention protrusion is formed to protrude out from a top of the sloping guide surfaces toward the one of the first plate part and the second plate part (14, 16), at the tip portion of the central guide protrusion, the engagement prevention protrusion being provided at the position where the first and second plate parts open up as if opening its mouth between the edges on the opening side opposite the curved portion. a first plate part and a second plate part connected at a curved portion; compressive protrusions (22, 24) provided on opposing surfaces of the first plate part and the second plate part that close a medical tube by compression between them; and a locking means that elastically deforms the curved portion and retains the medical tube in a closed state by locking the first and second plate parts (14, 16) at a location close to each other, at least one of the first plate part and the second plate part has a pair of side walls on both sides that protrude out toward another of the first plate part and the second plate part, in order to prevent the medical tube from being displaced off sideways, the other of the first plate part and the second plate part has a central guide protrusion that protrudes out toward the one of the first plate part and the second plate part, the medical tube clamp being characterized in that both sides of a tip portion of the central guide protrusion protrude out toward a center to make sloping guide surfaces that guide the central guide protrusion into a gap between the pair of side walls while preventing interference against the pair of side walls during a relative displacement of the first and second plate parts (14, 16) in a direction of bringing them closer to each other, and an engagement prevention protrusion is formed to protrude out from a top of the sloping guide surfaces toward the one of the first plate part and the second plate part (14, 16), at the tip portion of the central guide protrusion, the engagement prevention protrusion being provided at the position where the first and second plate parts open up as if opening its mouth between the edges on the opening side opposite the curved portion.