The utility model discloses an oil well chemical feeding device and belongs to the technical field of oil extraction machines of oil fields. The oil well chemical feeding device comprises a first tubing nipple, a tank body, a screwed plug and an emptying valve. One end of the first tubing nipple is connected with an oil well casing valve, the other end of the first tubing nipple is connected with the emptying valve, a chemical dripping hole penetrating through the outer wall of the tubing nipple is formed in the first tubing nipple, and the emptying valve is used for releasing gas in the first tubing nipple. One end of the tank body is welded to the outer wall of the first tubing nipple, the chemical dripping hole is located in the tank body, an inner cavity of the tank body is communicated with an inner cavity of the first tubing nipple through the chemical dripping hole, a chemical feeding port communicated with the inner cavity of the tank body is formed in the other end of the tank body, and the screwed plug can cover the chemical charging port to seal the tank body. The oil well chemical feeding device can solve the problem that effective use of chemicals cannot be guaranteed and can guarantee effective use of chemicals. The oil well chemical feeding device is used for feeding chemicals for oil well casings.