A coil device for wireless power transmission and/or reception, comprising: a ground-side coil disposed on a road surface where a vehicle parks or stops and wirelessly transmitting or receiving electric power to or from a vehicle-side coil mounted on the vehicle;an information acquisition unit disposed around the ground-side coil and acquiring information relating to a position of the vehicle relative to the ground-side coil; a display unit; and a control unit controlling a display mode on the display unit, wherein the control unit has a position acquisition unit obtaining the position of the vehicle relative to the ground-side coil by using the information relating to the position, a position determination unit determining whether the vehicle is present in a first region or a second region (MR, ML) by using a result of the position acquisition unit, and a first display mode generation unit generating a display mode indicating that the vehicle is positioned in the first region to the driver in a case where the vehicle is present in the first region and generating a display mode indicating that the vehicle is positioned in the second region (MR, ML) to the driver in a case where the vehicle is positioned in the second region (MR, ML); and a housing accommodating the ground-side coil, the information acquisition unit, and the control unit; characterized in that the housing accommodates the display unit; the display unit is provided to a main surface of the housing, and disposed at a position visible to a driver of the vehicle approaching the ground-side coil, wherein the main surface faces a bottom surface of the vehicle; and the first region is a region where the vehicle-side coil is capable of reaching a position above the ground-side coil in a case where the vehicle travels straight along a reference axis passing through the ground-side coil, and the second region (MR, ML) is a region where the vehicle-side coil is incapable of reaching the position above of the ground-side coil in a case where the vehicle travels straight along the reference axis. a ground-side coil disposed on a road surface where a vehicle parks or stops and wirelessly transmitting or receiving electric power to or from a vehicle-side coil mounted on the vehicle;an information acquisition unit disposed around the ground-side coil and acquiring information relating to a position of the vehicle relative to the ground-side coil; a display unit; and a control unit controlling a display mode on the display unit, wherein the control unit has a position acquisition unit obtaining the position of the vehicle relative to the ground-side coil by using the information relating to the position, a position determination unit determining whether the vehicle is present in a first region or a second region (MR, ML) by using a result of the position acquisition unit, and a first display mode generation unit generating a display mode indicating that the vehicle is positioned in the first region to the driver in a case where the vehicle is present in the first region and generating a display mode indicating that the vehicle is positioned in the second region (MR, ML) to the driver in a case where the vehicle is positioned in the second region (MR, ML); and a position acquisition unit obtaining the position of the vehicle relative to the ground-side coil by using the information relating to the position, a position determination unit determining whether the vehicle is present in a first region or a second region (MR, ML) by using a result of the position acquisition unit, and a first display mode generation unit generating a display mode indicating that the vehicle is positioned in the first region to the driver in a case where the vehicle is present in the first region and generating a display mode indicating that the vehicle is positioned in the second region (MR, ML) to the driver in a case where the vehicle is positioned in the second region (MR, ML); and a housing accommodating the ground-side coil, the information acquisition unit, and the control unit; characterized in that the housing accommodates the display unit; the display unit is provided to a main surface of the housing, and disposed at a position visible to a driver of the vehicle approaching the ground-side coil, wherein the main surface faces a bottom surface of the vehicle; and the first region is a region where the vehicle-side coil is capable of reaching a position above the ground-side coil in a case where the vehicle travels straight along a reference axis passing through the ground-side coil, and the second region (MR, ML) is a region where the vehicle-side coil is incapable of reaching the position above of the ground-side coil in a case where the vehicle travels straight along the reference axis.