Outer conductor terminal and shield connector

An external conductor terminal (22) comprises: a terminal body (45) that can surround the outer periphery of an internal conductor terminal (21); a back plate part (43) that is displaced from an open state to a closed state in relation to the terminal body (45), and seals a back-surface opening of the terminal body (45) in the closed state; and a side plate part (44) that connects to the back plate part (43), and constitutes a part of a side-surface portion of the terminal body (45) in the closed state. The back plate part (43) has a base plate connection piece (49) that projects out toward a circuit board (90). The side plate part (44) has: a linear-shaped slit (53) that extends toward the circuit board (90); and a locking part (54) that is bent and raised through the slit (53), is locked to the terminal body (45), and holds the back plate part (43) in the closed state.