A pressure adjusting device of a sprayer spraying gun comprises the spraying gun of a sprayer and is characterized in that a pressure adjusting valve is arranged in the spraying gun, the pressure adjusting valve comprises a valve body, a valve cavity is arranged in the valve body, a hollow column is arranged in the valve cavity, the hollow column divides the valve cavity into an outer valve cavity and an inner valve cavity, a left connector, a right connector and an upper connector are arranged on the valve body, the left connector and the right connector are connected with the spraying gun respectively, the upper connector is connected with a spring cap, a film piece is arranged in the upper connector, the lower face of the film piece is in contact with the hollow column, a valve element is arranged in the upper connector on the upper face of the film piece, a spring is arranged on the valve element, one end of the spring is in contact with the valve element, and the other end of the spring is in contact with the inner wall of the spring cap.