A ball feeding device includes a mounting seat with a driving device. The driving device includes a driving shaft defining an axis of rotation. A discharge hole is provided in a top plate of the mounting seat. An annular guiding wall is formed on the top plate and surrounds the axis of rotation. A rotary unit is rotatably mounted on the top plate and includes tubes for containing balls. A blocking member is mounted in each tube. When the rotary unit is rotated, lower ends of the tubes are aligned with the discharge hole in sequence such that the balls in the tubes are fed into a pitching machine one by one. The blocking members hold or release the balls in the tubes under the action of the guiding wall such that the balls to be fed cannot contact with the top plate.