A roof box comprising: a roof box body having a storage portion and an openable/closable cover; lock mechanisms provided in both sides of the roof box body along a travel direction to engage and fasten the storage portion and the openable/closable cover while the roof box body is mounted; fastening release means installed in each of the lock mechanisms provided in both sides of the roof box body to release the engagement and fastening; opening/closing means configured to open or close the openable/closable cover with respect to any one of the lock mechanisms when the engagement and fastening of the other lock mechanism is released; a manipulation means configured to transmit an opening/closing operation signal for selection of the lock mechanisms for releasing the engagement and fastening and opening/closing of the openable/closable cover using the opening/closing means; characterized by a control means configured to receive the opening/closing operation signal from the manipulation means, output an engagement release signal to the selected one of the lock mechanisms, and output an opening/closing signal for releasing the openable/ closable cover to the opening/closing means after the engagement is released; and an opened/closed state detection means that detects a side in which the openable/closable cover is released, wherein the control means determines whether or not a side where engagement of the lock mechanism is released matches a side detected by the opened/closed state detection means as being released, and a command signal for stopping an opening/closing operation of the openable/closable cover is output to the opening/closing means if the sides do not match as a result of the determination. a roof box body having a storage portion and an openable/closable cover; lock mechanisms provided in both sides of the roof box body along a travel direction to engage and fasten the storage portion and the openable/closable cover while the roof box body is mounted; fastening release means installed in each of the lock mechanisms provided in both sides of the roof box body to release the engagement and fastening; opening/closing means configured to open or close the openable/closable cover with respect to any one of the lock mechanisms when the engagement and fastening of the other lock mechanism is released; a manipulation means configured to transmit an opening/closing operation signal for selection of the lock mechanisms for releasing the engagement and fastening and opening/closing of the openable/closable cover using the opening/closing means; characterized by a control means configured to receive the opening/closing operation signal from the manipulation means, output an engagement release signal to the selected one of the lock mechanisms, and output an opening/closing signal for releasing the openable/ closable cover to the opening/closing means after the engagement is released; and an opened/closed state detection means that detects a side in which the openable/closable cover is released, wherein the control means determines whether or not a side where engagement of the lock mechanism is released matches a side detected by the opened/closed state detection means as being released, and a command signal for stopping an opening/closing operation of the openable/closable cover is output to the opening/closing means if the sides do not match as a result of the determination.