A modular side-by-side vise structure including a base, a fixture block group located on the base, and a side clamping piece group; the side clamping piece has an upper part and a lower part, and a bolt is screwed in the upper part to prop the lower part, so that the stopper and movable fixture block cling to the base tightly; or the side grooves on both sides of the stopper and movable fixture block are provided with bolt holes, and the inner wall of side clamping piece is provided with a punch hole, the bolt is screwed in the bolt hole through the punch hole, so that the stopper and movable fixture block cling to the base tightly. Therefore, it is unnecessary to hold up the side clamping piece with a hand while tightening or loosening the bolt, favorable for the technician to implement quick assembly or disassembly.