Provided are a rubber sheet member joining device and method. At least one opposing surface of a pair of gripping parts is provided with a contact member having a contact surface projecting toward an other opposing surface of the pair of gripping parts; the pair of gripping parts grip ranges in proximity to end surfaces in a state in which end surfaces project from the one opposing surface toward the other opposing surface; the total of end surface projection amounts of the end surfaces from the opposing surfaces is set to be a predetermined length larger than a separation distance between the opposing surfaces when the contact member is sandwiched between the opposing surfaces; and by bringing the contact member into a state of being sandwiched between the opposing surfaces, the movement of the gripping parts in proximity to each other is stopped and the end surfaces are joined together.