Abstract: A pitcher protection net device in baseball practice having a frame installed on the ground to vertically extend to cover a pitcher from his front. A net closes a space surrounded by the outer edge of the frame and is attached to the frame. The frame includes a main frame forming one lateral portion on one widthwise side. An auxiliary frame projects from the lower portion of the main frame toward the other widthwise side to form the other lateral portion of the frame. The pitcher protection net device in baseball practice includes an extension net that closes a corner space surrounded by this side edge of the upper portion main frame on the other side and the upper edge of the auxiliary frame. The extension net is capable of deflecting downward. The pitcher protection net device also includes an adjusting means for adjusting the amount of deflection of the upper edge to the extension net.