A connector box comprising: a receptacle connector portion having a connector insertion opening which is configured to receive a plug connector inserted from the front side; a circuit board unit having the receptacle connector portion at a front end of a circuit board; a casing configured to accommodate the circuit board unit with the connector insertion opening being opened to the outside; and a light guiding lens for guiding light to the outside of the casing; the light guiding lens including an annular portion fitted to an outer side of the receptacle connector portion and a pair of retaining portions extending rearwards from the annular portion; the circuit board unit including a light emitting portion disposed in an upper face portion of the circuit board and optically coupled with at least one of the pair of retaining portions the casing including a lower casing for covering a lower face of the circuit board unit and an upper casing for covering an upper face of the circuit board unit and engaged with the lower casing, the circuit board unit being fixed to the upper casing; the upper casing having a front end wall and a retaining hole extending through the front end wall in a front/rear direction; and the lower casing including a front face plate portion having an opening portion which is configured to receive the receptacle connector portion inserted and which is configured to open the connector insertion opening to the outside of the casing; characterized in that the upper casing has a receptacle connector accommodating portion for accommodating at least a portion of the receptacle connector portion; and that the annular portion includes an annular lens portion fitted to an outer side of the receptacle connector portion and a light guiding edge portion extending to an outer side in a circumferential direction from the annular lens portion; and that the light guiding lens being mounted to the upper casing with the retaining portions thereof being inserted in the retaining hole and the light guiding lens being fixed to the casing with the light guiding edge portion thereof being clamped between the front end wall and the front face plate portion. a receptacle connector portion having a connector insertion opening which is configured to receive a plug connector inserted from the front side; a circuit board unit having the receptacle connector portion at a front end of a circuit board; a casing configured to accommodate the circuit board unit with the connector insertion opening being opened to the outside; and a light guiding lens for guiding light to the outside of the casing; the light guiding lens including an annular portion fitted to an outer side of the receptacle connector portion and a pair of retaining portions extending rearwards from the annular portion; the circuit board unit including a light emitting portion disposed in an upper face portion of the circuit board and optically coupled with at least one of the pair of retaining portions the casing including a lower casing for covering a lower face of the circuit board unit and an upper casing for covering an upper face of the circuit board unit and engaged with the lower casing, the circuit board unit being fixed to the upper casing; the upper casing having a front end wall and a retaining hole extending through the front end wall in a front/rear direction; and the lower casing including a front face plate portion having an opening portion which is configured to receive the receptacle connector portion inserted and which is configured to open the connector insertion opening to the outside of the casing; characterized in that the upper casing has a receptacle connector accommodating portion for accommodating at least a portion of the receptacle connector portion; and that the annular portion includes an annular lens portion fitted to an outer side of the receptacle connector portion and a light guiding edge portion extending to an outer side in a circumferential direction from the annular lens portion; and that the light guiding lens being mounted to the upper casing with the retaining portions thereof being inserted in the retaining hole and the light guiding lens being fixed to the casing with the light guiding edge portion thereof being clamped between the front end wall and the front face plate portion.