An electromagnetic wave sensor cover configured to be employed in an electromagnetic wave sensor including a transmitting portion that transmits an electromagnetic wave in form of infrared rays and a receiving portion that receives the electromagnetic wave the electromagnetic wave sensor cover comprising a cover body (20; 34; 41; 42) configured to cover the transmitting portion and the receiving portion from a front in a transmission direction of the electromagnetic wave from the transmitting portion, wherein the cover body (20; 34; 41; 42) includes: a base layer made of synthetic resin and permitting passage of the electromagnetic wave; a metal oxide layer permitting passage of the electromagnetic wave and being conductive; a low refractive index layer permitting passage of the electromagnetic wave; and two electrodes disposed in contact with the metal oxide layer to energize the metal oxide layer so that the metal oxide layer generates heat, the base layer includes a front surface and a rear surface in the transmission direction, the metal oxide layer and the low refractive index layer are laminated adjacent to each other in the transmission direction, a laminate of the metal oxide layer and the low refractive index layer is laminated on the rear surface of the base layer, and the low refractive index layer is laminated adjacent to a rear surface of the metal oxide layer in the transmission direction and made of material that has a lower refractive index than material of the metal oxide layer so that a reflected wave of the electromagnetic wave reflected on a boundary of an air layer and the low refractive index layer and a reflected wave of the electromagnetic wave reflected on a boundary of the low refractive index layer and the metal oxide layer interfere with each other and weaken each other. and a receiving portion that receives the electromagnetic wave the electromagnetic wave sensor cover comprising a cover body (20; 34; 41; 42) configured to cover the transmitting portion and the receiving portion from a front in a transmission direction of the electromagnetic wave from the transmitting portion, wherein the cover body (20; 34; 41; 42) includes: a base layer made of synthetic resin and permitting passage of the electromagnetic wave; a metal oxide layer permitting passage of the electromagnetic wave and being conductive; a low refractive index layer permitting passage of the electromagnetic wave; and two electrodes disposed in contact with the metal oxide layer to energize the metal oxide layer so that the metal oxide layer generates heat, a base layer made of synthetic resin and permitting passage of the electromagnetic wave; a metal oxide layer permitting passage of the electromagnetic wave and being conductive; a low refractive index layer permitting passage of the electromagnetic wave; and two electrodes disposed in contact with the metal oxide layer to energize the metal oxide layer so that the metal oxide layer generates heat, the base layer includes a front surface and a rear surface in the transmission direction, the metal oxide layer and the low refractive index layer are laminated adjacent to each other in the transmission direction, a laminate of the metal oxide layer and the low refractive index layer is laminated on the rear surface of the base layer, and the low refractive index layer is laminated adjacent to a rear surface of the metal oxide layer in the transmission direction and made of material that has a lower refractive index than material of the metal oxide layer so that a reflected wave of the electromagnetic wave reflected on a boundary of an air layer and the low refractive index layer and a reflected wave of the electromagnetic wave reflected on a boundary of the low refractive index layer and the metal oxide layer interfere with each other and weaken each other.