A photoelectric smoke detector which includes an explosion-proof enclosure in which a circuit compartment capable of housing an electronic circuit board is contained, a light-emitting device and a light-receiving device, wherein the light-emitting device and the light-receiving device are able to be exposed to smoke generated by an explosion, wherein the light-emitting device comprises: a first hollow cylindrical member having a tubular wall with a first inner face, and a first opening through which a first internal space enclosed by the first inner face of the tubular wall communicates with the circuit compartment; a light-emitting element placed on a bottom of the first hollow cylindrical member that borders the first internal space and faces the first opening; and a first transparent member for transmitting light emitted by the light-emitting element, wherein the light-receiving device comprises: a second hollow cylindrical member having a tubular wall with a second inner face, and a second opening through which a second internal space enclosed by the second inner face of the tubular wall communicates with the circuit compartment; a light-receiving element placed on a bottom of the second hollow cylindrical member that borders the second internal space and faces the second opening; and a second transparent member for guiding light to the light-receiving element, and wherein a gap between the first inner face and the first transparent member has a first width, and a gap between the second inner face and the second transparent member has a second width, where the first width and the second width are 0.1 mm or less, and wherein a portion of the first transparent member between the first opening and a light-exiting end of the first transparent member has a first length along an axis of the first transparent member and a portion of the second transparent member between the second opening and an light-entering end of the second transparent member has a second length along an axis of the second transparent member, where the first length and the second length are 9.5 mm or more. a first hollow cylindrical member having a tubular wall with a first inner face, and a first opening through which a first internal space enclosed by the first inner face of the tubular wall communicates with the circuit compartment; a light-emitting element placed on a bottom of the first hollow cylindrical member that borders the first internal space and faces the first opening; and a first transparent member for transmitting light emitted by the light-emitting element, wherein the light-receiving device comprises: a second hollow cylindrical member having a tubular wall with a second inner face, and a second opening through which a second internal space enclosed by the second inner face of the tubular wall communicates with the circuit compartment; a light-receiving element placed on a bottom of the second hollow cylindrical member that borders the second internal space and faces the second opening; and a second transparent member for guiding light to the light-receiving element, and a second hollow cylindrical member having a tubular wall with a second inner face, and a second opening through which a second internal space enclosed by the second inner face of the tubular wall communicates with the circuit compartment; a light-receiving element placed on a bottom of the second hollow cylindrical member that borders the second internal space and faces the second opening; and a second transparent member for guiding light to the light-receiving element, and wherein a gap between the first inner face and the first transparent member has a first width, and a gap between the second inner face and the second transparent member has a second width, where the first width and the second width are 0.1 mm or less, and wherein a portion of the first transparent member between the first opening and a light-exiting end of the first transparent member has a first length along an axis of the first transparent member and a portion of the second transparent member between the second opening and an light-entering end of the second transparent member has a second length along an axis of the second transparent member, where the first length and the second length are 9.5 mm or more.