A refrigerator includes a cabinet, a door including a door frame with an opening, a panel assembly provided at the opening and configured to allow an inside of the refrigerator to be seen through the panel assembly from an outside of the refrigerator, a knock detection device configured to detect a user's knocking operation on the panel assembly, and a lighting unit provided inside the refrigerator and configured to turn on or off based on a signal of the knock detection device while the door is closed. The panel assembly includes a front panel, an insulation panel spaced apart from a rear surface of the front panel, and a spacer bar provided between the front panel and the insulation panel. An insulation space is defined between the front panel and the insulation panel, and the knock detection device is provided outside the insulation space.