A connector assembly comprising: a first connector having a first housing on which an elastic locking piece is suspended; a second connector having a second housing on which a locking member configured to be mated with the elastic locking piece is formed so as to lock the first and second connectors (100, 200) together when the first and second connectors (100, 200) are mated with each other; and a connector position assurance device having a first stopper and a second stopper behind the first stopper, wherein a first mating stopper is formed on the elastic locking piece, and a second mating stopper is formed on the first housing of the first connector, wherein the connector position assurance device is configured to be inserted into a first position under the elastic locking piece of the first connector when the first and second connectors (100, 200) are separate from each other, wherein at the first position, the first stopper of the connector position assurance device is abutted against the first mating stopper of the first connector to prevent the connector position assurance device from being further pushed forward, and at the first position, the second stopper of the connector position assurance device is abutted against the second mating stopper of the first connector to prevent the connector position assurance device from being pulled out backward, characterized in that the connection position assurance device further comprises: a pair of elongated arms (301, 302) separated from each other by a spacing slot; and a bottom plate recessedly disposed between the pair of elongated arms at a rear portion of the spacing slot, wherein the first stopper is configured to be a protrusion projected upward from the bottom plate; wherein the first mating stopper is configured to be an elastic finger formed in an opening of the elastic locking piece and extending aslant and downward beyond a bottom surface of the elastic locking piece, wherein the second stopper is configured to be an elastic finger formed in an opening of the bottom plate of the connector position assurance device and extending aslant and downward beyond a bottom surface of the bottom plate; and wherein the second mating stopper is configured to be a protrusion projected upward from the first housing of the first connector. a first connector having a first housing on which an elastic locking piece is suspended; a second connector having a second housing on which a locking member configured to be mated with the elastic locking piece is formed so as to lock the first and second connectors (100, 200) together when the first and second connectors (100, 200) are mated with each other; and a connector position assurance device having a first stopper and a second stopper behind the first stopper, wherein a first mating stopper is formed on the elastic locking piece, and a second mating stopper is formed on the first housing of the first connector, wherein the connector position assurance device is configured to be inserted into a first position under the elastic locking piece of the first connector when the first and second connectors (100, 200) are separate from each other, wherein at the first position, the first stopper of the connector position assurance device is abutted against the first mating stopper of the first connector to prevent the connector position assurance device from being further pushed forward, and at the first position, the second stopper of the connector position assurance device is abutted against the second mating stopper of the first connector to prevent the connector position assurance device from being pulled out backward, characterized in that the connection position assurance device further comprises: a pair of elongated arms (301, 302) separated from each other by a spacing slot; and a bottom plate recessedly disposed between the pair of elongated arms at a rear portion of the spacing slot, a pair of elongated arms (301, 302) separated from each other by a spacing slot; and a bottom plate recessedly disposed between the pair of elongated arms at a rear portion of the spacing slot, wherein the first stopper is configured to be a protrusion projected upward from the bottom plate; wherein the first mating stopper is configured to be an elastic finger formed in an opening of the elastic locking piece and extending aslant and downward beyond a bottom surface of the elastic locking piece, wherein the second stopper is configured to be an elastic finger formed in an opening of the bottom plate of the connector position assurance device and extending aslant and downward beyond a bottom surface of the bottom plate; and wherein the second mating stopper is configured to be a protrusion projected upward from the first housing of the first connector.