Abstract: Cavities (21) into which terminal fittings (10) are insertable from behind are arranged at upper and lower stages in a housing (20), and locks (28) are provided at the lower surfaces of the respective cavities (21). Each lock (28) is formed by cutting a partition wall (22) partitioning the upper and lower cavities (21) or a bottom wall (23) of the housing (20), and includes an arm (29) supported at both front and rear ends. A locking section (30) engageable with an engaging edge (15) of the corresponding terminal fitting (10) is provided on the upper surface of each arm portion (29) to project into the cavity (21). When the terminal fitting (10) is inserted into the cavity (21), the locking section (30) is pushed by the terminal fitting (10) to resiliently deform the arm (29) into a substantially arched shape with its coupled portions at the front and rear ends as supporting points.