Looseness of two housings are suppressed. A connector includes a lower housing and an upper housing. The lower housing is provided with a locking portion. The upper housing is provided with an elastic locking piece that is hooked on the locking portion. The elastic locking piece has a cantilever shape, and restricts relative movement of the lower housing and the upper housing in a separation direction, which is a direction opposite to a coupling direction. The lower housing is provided with a protruding piece portion that protrude outward in a left-right direction. The upper housing is provided with a protruding piece restriction portion that restricts movement of the protruding piece portion. The protruding piece restriction portion is provided with an inclined surface that is inclined in an assembly direction to reduce a movable range of the protruding piece portion in a separation direction.