A connector assembly comprising: a first connector which comprises a tubular outer housing and an inner housing received in the outer housing and in which a plurality of first terminals are provided in the inner housing; a second connector which comprises a counterpart housing having a bottomed tubular shape and configured to receive the inner housing at a time of being inserted into the outer housing and in which a plurality of second terminals are provided in an inner surface of a bottom portion of the counterpart housing; an elastic member which is provided in the outer housing and urges the inner housing toward a front side of the first connector in a fitting direction; and a lock member which is provided in an opening end of the counterpart housing, characterized in that the connector assembly further comprises a first projection which is provided in an inner surface of the outer housing and a second projection which is provided in an outer surface of the inner housing, wherein in a middle of fitting the first connector and the second connector, the lock member abuts on the first projection so as to be deformed elastically in a direction toward the inner housing and butts the second projection to retreat the inner housing to a back surface of the first connector in the fitting direction against an urging force of the elastic member, and wherein at a time of completely fitting the first connector and the second connector, the lock member receives the first projection in a hole part provided in the lock member so as to elastically return in a direction away from the inner housing, and the lock member is released from butting the second projection such that the elastic member is allowed to elastically return to move the inner housing to the front side of the first connector, so that the inner housing is guided toward the bottom portion of the counterpart housing, and the first terminal and the second terminal are connected with each other. a first connector which comprises a tubular outer housing and an inner housing received in the outer housing and in which a plurality of first terminals are provided in the inner housing; a second connector which comprises a counterpart housing having a bottomed tubular shape and configured to receive the inner housing at a time of being inserted into the outer housing and in which a plurality of second terminals are provided in an inner surface of a bottom portion of the counterpart housing; an elastic member which is provided in the outer housing and urges the inner housing toward a front side of the first connector in a fitting direction; and a lock member which is provided in an opening end of the counterpart housing, characterized in that the connector assembly further comprises a first projection which is provided in an inner surface of the outer housing and a second projection which is provided in an outer surface of the inner housing, wherein in a middle of fitting the first connector and the second connector, the lock member abuts on the first projection so as to be deformed elastically in a direction toward the inner housing and butts the second projection to retreat the inner housing to a back surface of the first connector in the fitting direction against an urging force of the elastic member, and wherein at a time of completely fitting the first connector and the second connector, the lock member receives the first projection in a hole part provided in the lock member so as to elastically return in a direction away from the inner housing, and the lock member is released from butting the second projection such that the elastic member is allowed to elastically return to move the inner housing to the front side of the first connector, so that the inner housing is guided toward the bottom portion of the counterpart housing, and the first terminal and the second terminal are connected with each other.