A connector (10) has a terminal accommodating portion (31) with a plurality of cavities (34) into which terminals (20) are accommodated from behind and a front holder (50) is mounted into the terminal accommodating portion (31). The front holder (50) includes locks (53) that move onto locked portions (49) on the upper surface of a narrow portion (45) of the terminal accommodating portion (31) when the front holder (50) is mounted into the terminal accommodating portion (31). The narrow portion (45) includes deformation preventing recesses (47) that fit to deformation preventing ribs (57) on the front holder (50) in a convexo-concave manner. The deformation preventing ribs (57) and the deformation preventing recesses (47) contact each other in a vertical direction when the locks (53) move onto the locked portions (49), thereby suppressing excessive deflection of the front holder (50) or the narrow portion (45).