A connector mateable with a mating connector along a front-rear direction, wherein: the mating connector comprises a mating lock portion; the connector comprises a plurality of contacts, a holding member and a mid-plate; the contacts form two contact rows(160, 170); the contacts forming each of the contact rows are aligned in a pitch direction perpendicular to the front-rear direction; the contact rows are arranged apart from each other in an up-down direction perpendicular to both of the front-rear direction and the pitch direction; the holding member comprises a holding portion and a mating portion; the holding portion holds the contacts; the mating portion has a tongue-like shape and extends forward from the holding portion; the holding member is formed with two accommodation portions, a middle portion and regulating portions; the accommodation portions extend forward from a rear end of the holding member and open outward in the pitch direction at the mating portion; the middle portion is situated between the accommodation portions in the pitch direction; the regulating portions are formed in the mating portion; the mid-plate comprises two flat plate portions; and the flat plate portions are accommodated by the accommodation portions, respectively, and the middle portion is sandwiched between the flat plate portions in the pitch direction; characterized in that each of the flat plate portions comprises a base portion, a press-fit portion, a spring portion, a lock portion and a regulated portion; the press-fit portion protrudes from the base portion in the pitch direction and is pressed against the holding portion; the spring portion extends forward from the base portion and has resilience; the spring portion is apart from the regulating portions in the pitch direction; the lock portion is supported by the spring portion and protrudes outward of the mating portion in the pitch direction; the regulated portion extends forward from the base portion and is situated inward of the regulating portions in the pitch direction; and the lock portion and the mating lock portion lock a mated state of the connector and the mating connector. the mating connector comprises a mating lock portion; the connector comprises a plurality of contacts, a holding member and a mid-plate; the contacts form two contact rows(160, 170); the contacts forming each of the contact rows are aligned in a pitch direction perpendicular to the front-rear direction; the contact rows are arranged apart from each other in an up-down direction perpendicular to both of the front-rear direction and the pitch direction; the holding member comprises a holding portion and a mating portion; the holding portion holds the contacts; the mating portion has a tongue-like shape and extends forward from the holding portion; the holding member is formed with two accommodation portions, a middle portion and regulating portions; the accommodation portions extend forward from a rear end of the holding member and open outward in the pitch direction at the mating portion; the middle portion is situated between the accommodation portions in the pitch direction; the regulating portions are formed in the mating portion; the mid-plate comprises two flat plate portions; and the flat plate portions are accommodated by the accommodation portions, respectively, and the middle portion is sandwiched between the flat plate portions in the pitch direction; characterized in that each of the flat plate portions comprises a base portion, a press-fit portion, a spring portion, a lock portion and a regulated portion; the press-fit portion protrudes from the base portion in the pitch direction and is pressed against the holding portion; the spring portion extends forward from the base portion and has resilience; the spring portion is apart from the regulating portions in the pitch direction; the lock portion is supported by the spring portion and protrudes outward of the mating portion in the pitch direction; the regulated portion extends forward from the base portion and is situated inward of the regulating portions in the pitch direction; and the lock portion and the mating lock portion lock a mated state of the connector and the mating connector.