The present invention discloses a device for detecting x-rays inside the mouth, which can be conveniently moved inside the mouth, can increase user convenience, and has improved economic feasibility. The device for detecting x-rays inside the mouth according to the present invention comprises: a sensor unit having a sensor built therein for detecting x-rays; a hinge unit formed on one surface of the sensor unit; and a cable connecting unit including a pivoting connecting portion having an external cable coupled thereto and coupled to be pivotable to the hinge unit. An internal cable withdrawn from the sensor unit is electrically connected to the external cable through the inside of the cable connecting unit by means of the hinge unit and the pivoting connecting portion.