A connector connectable to a counterpart connector having pin terminals and attachable to a flat cable at an end thereof having lands for electrical contacts, the connector comprising: a housing including a plate-shaped portion and a terminal accommodating portion continuous with the plate-shaped portion, the terminal accommodating portion having accommodating holes, each of the accommodating holes penetrating through the terminal accommodating portion and having an end opening to the plate-shaped portion; and socket terminals respectively held in the accommodating holes, each of the socket terminals including a box portion and a spring portion, the box portion being used for receiving a corresponding one of the pin terminals of the counterpart connector, and the spring portion having a cantilever shape and extending from the box portion, through the end of a corresponding one of the accommodating holes, onto the plate-shaped portion, wherein the spring portion includes a slope portion and a contact portion, the slope portion extending from the box portion, the contact portion is configured to, in response to insertion of the end of the flat cable, separate from the plate-shaped portion in order to make space for the end of the flat cable, and the contact portion is configured to make contact with a corresponding one of the lands of the flat cable after the insertion of the end of the flat cable, characterized in that each of the accommodating holes of the terminal accommodating portion has, at an inner surface thereof, a protrusion protruding from the inner surface, the spring portion further includes a horizontal portion following the slope portion, the contact portion follows the horizontal portion, the horizontal portion is configured to make contact with the protrusion only after the insertion of the end of the flat cable, and thereby movement of the horizontal portion is restricted by the protrusion, and only after the insertion of the end of the flat cable, the protrusion serves as a supporter to make the horizontal portion be a support point located between a base end of the spring portion and a free end of the spring portion, and receives the part of force that the spring portion receives from the flat cable. a housing including a plate-shaped portion and a terminal accommodating portion continuous with the plate-shaped portion, the terminal accommodating portion having accommodating holes, each of the accommodating holes penetrating through the terminal accommodating portion and having an end opening to the plate-shaped portion; and socket terminals respectively held in the accommodating holes, each of the socket terminals including a box portion and a spring portion, the box portion being used for receiving a corresponding one of the pin terminals of the counterpart connector, and the spring portion having a cantilever shape and extending from the box portion, through the end of a corresponding one of the accommodating holes, onto the plate-shaped portion, wherein the spring portion includes a slope portion and a contact portion, the slope portion extending from the box portion, the contact portion is configured to, in response to insertion of the end of the flat cable, separate from the plate-shaped portion in order to make space for the end of the flat cable, and the contact portion is configured to make contact with a corresponding one of the lands of the flat cable after the insertion of the end of the flat cable, characterized in that each of the accommodating holes of the terminal accommodating portion has, at an inner surface thereof, a protrusion protruding from the inner surface, the spring portion further includes a horizontal portion following the slope portion, the contact portion follows the horizontal portion, the horizontal portion is configured to make contact with the protrusion only after the insertion of the end of the flat cable, and thereby movement of the horizontal portion is restricted by the protrusion, and only after the insertion of the end of the flat cable, the protrusion serves as a supporter to make the horizontal portion be a support point located between a base end of the spring portion and a free end of the spring portion, and receives the part of force that the spring portion receives from the flat cable.