An electric connector includes a housing having a groove configured to receive a signal-transmission medium, and a lock device including a locker configured to lock the signal-transmission medium at the groove, the locker being configured to move up beyond and down below a first inner surface of the groove extending in parallel with a direction in which the signal-transmission medium is received in the groove, the locker being energized towards a second inner surface of the groove, the second inner surface being disposed opposite to the first inner surface, and the lock device further including a compressor configured to compress the signal-transmission medium towards the second inner surface.