To provide a water saving valve which achieves labor saving in manufacturing and the prevention of a theft in use by simplifying a valve structure of a flow control valve.

In the water saving valve A, a sluice block is incorporated in a water passing chamber of a joint metal 1 joined to a mouth end of a faucet. In the sluice block, a sluice panel provided with a butterfly blade, and a water passing panel having a required number of water passing holes point-symmetrically opened in the center are joined to each other in an overlapping state in a flow rate-adjustable manner. A foam generating body 5 is spirally provided at the lower end of the joint metal 1, the water passing panel of the sluice block is pressed and internally fitted into the step of the water passing chamber, and the foam generating body 5 forms a required gap 6 between an upper end thereof and a lower end of a peripheral portion of the joint metal 1. In the antitheft water saving valve B, the water saving valve A in which a seating panel 8b peripherally provided at the inner periphery of a cylindrical cylinder body 8a is loosely fitted into the gap 6 and which comprises the joint metal 1 and the foam generating body 5 is housed in an antitheft cylinder 8.