A coupling device which contributes to a further reduction in the space required to transport a die etc., in which first and second joints are simplified in structure and downsized, and that is advantageous when multiple sets of such first and second joints are installed. The coupling device comprises a female joint and a male joint. The female joint is fitted on a mold and comprises a first valve casing, a first valve body, and a first open/close valve having a first valve seat and a first valve portion. The male joint is fitted on a clamping plate of an injection molding machine and comprises a second valve casing, a second valve body, and a second open/close valve having a second valve seat and a second valve portion. The coupling device further comprises a valve body drive unit. When, in a condition where the front ends of the first and second valve casings and are in contact with each other, the valve body drive unit drives and advances, in the male joint, only the second valve body relative to the second valve casing, the first and second valve bodies and are driven to the valve opening side.