The nailing machine with safety mechanism is located between fastener and nailing part of nailing machine. The safety mechanism includes an adjustable shelf, which shifts recurrently within a limited range. The first end of adjustable shelf is linked to the fastener, and second end extends towards nailing part. One side of retainer is normally protruded from exterior of nailing part, and the other side extends towards adjustable shelf. The revolving controller is provided with a pin joint and a revolving end. The revolving end will limit and fix simultaneously adjustable shelf and retainer, or, in the case of second swinging angle, the revolving end will release adjustable shelf and retainer. When an idle nailing machine is firstly withheld by a fastener, the adjustable shelf will shift outwards, and then drive revolving end of revolving controller to separate from the adjustable shelf.