A valve with a locking mechanism and an integrated valve are provided. The valve includes a handle body having a knob, the handle body being disposed rotatably on top of a valve body housing a valve shaft for opening and closing a valve piece. A cutout stepped face is formed on a part of the outer periphery of the valve body located under the handle body. A locking plate having a locking hole is placed rotatably in the cutout stepped face via a pivotally attaching portion, and when the locking plate is rotated to either a position at which the valve body is in a full-close state or a position at which the valve body is in a full-open state, the locking hole is faced the upper surface area of the valve body to allow locking.