A compact valve using a shape memory alloy comprises: a moving valve body that contacts an inner periphery of a guide pipe having an built-in orifice, is freely movable and has a sealing portion to seal the orifice; a biasing coil provided between the orifice and the moving valve body; and a wire formed of a shape memory alloy and held between a stationary electrode of the guide pipe and a moving electrode of the moving valve body. The orifice is sealed by moving the moving valve body due to transformation of the shape memory alloy by heating the wire. The moving valve body is enabled to be elastically deformable by providing a coil spring to reduce a stress, so that an overload to the moving valve body due to contraction of the wire is absorbed by elastic deformation of the moving valve body. Thereby, the overload to the shape memory alloy is reduced to prevent deterioration of repeatability of memorized shape, to increase durability and reliability of the valve.