A movable member is provided at a flat conductor insertion location on one side in the connector thickness direction; at least either restricting portions or restricted protrusions have oblique surfaces rearwardly sloped toward the other side in the connector thickness direction; upon complete insertion of the flat conductor, engaging portions are positioned to be engageable with engaged portions in the direction of disengagement of the flat conductor at locations rearward of said engaged portions of the flat conductor; and, when a rearward disengagement force acts on the flat conductor upon complete insertion of said flat conductor, the engaged portions of the flat conductor engage the engaging portions and the restricted protrusions abut the restricting portions, as a result of which at least a reaction force directed toward the other side in the connector thickness direction is received from the restricting portions.