A wiper arm including an arm head having an arm head body and cover member. The cover member is attached to the arm head body and can open and close. The mechanical strength of the arm head can be increased. The arm head includes a head cap which is rotatably attached to rotating shafts and provided on the inner side surfaces of both side sidewalls of an arm head body. When the head cap is in its closed position, a front-side half section of the head cap is disposed between both side sidewalls. On the rear surface of a rear-side half section of the head cap, a cylindrical cap-side fitting section is provided and fits with a nut disposed on the arm head body. The cap-side fitting section includes slits and is formed so that the height in its vertical direction decreases in a front-side portion.