Medium feed device and image forming apparatus with suction-member moving mechanism

A medium feed device includes a suction member that sucks a medium on a stack member, a surrounding member supported movably in directions toward and away from the stack member together with the medium by suction, a stack-member moving mechanism, a suction-member moving mechanism, a transport member that transports the medium, a detected part associated with the surrounding member, a detecting part that is supported at the suction-member body and detects the detected part, a detector that detects a medium surface position based on a detection result of the detected part detected by the detecting part if the surrounding member moves toward the suction-member body from a state in which the medium contacts the surrounding member. The stack-member moving mechanism moves the stack member based on the medium surface position.