To provide a valve element unit and a gate valve apparatus which realize a reduction in manufacturing cost by a compact and simple structure and smooth rotary driving of the valve element without greatly moving the valve element in the direction of the center of rotation when the valve element is rotary driven.When a valve element unit 52 is rotary driven by valve element driving mechanisms 54, a rotary drive radius R2 of longitudinal both end sides of a first valve element 56 is smaller than a rotary drive radius R1 of a longitudinal center side of the first valve element 56. Therefore, even when a sidewall is formed on a longitudinal outer side of a transfer port 46 of a casing 44, part of the valve element unit 52 does not come into contact (interfere) with the sidewall, which makes it possible to rotary drive the valve element unit 52 only by slightly moving the valve element unit 52 in a direction of the center of rotation, without greatly moving the valve element unit 52 in the direction of the center of rotation at the time of the rotary driving.