A light-emitting-element housing member (1, 21, 41, 61, 81, 101A) comprising: a bottom base material (7, 27, 47, 67, 87) that includes a first surface (7a, 27a, 47a, 67a, 87a), and a mounting part (12, 32, 52, 72, 92) on the first surface (7a, 27a, 47a, 67a, 87a) on which a light emitting element (3, 23, 43, 63, 83) is to be mounted; and a frame member (9, 29, 49, 69, 89) that includes side walls (9a, 9b, 9c, 9d, 29a, 29b, 29c, 29d, 49a, 49c, 69a, 69b, 69c, 69d, 89a, 89b, 89c, 89d) erected on the first surface (7a, 27a, 47a, 67a, 87a) to surround the mounting part (12, 12a, 32, 52, 72, 92), and an opening (15, 35, 55, 75, 95) that penetrates through one of the side walls (9a, 29a, 49a, 69a, 89a) and is configured to transmit light emitted from the light emitting element (3, 23, 43, 63, 83) to the outside of the light-emitting-element housing member (1, 21, 41, 61, 81, 101A), wherein the opening (15, 35, 55, 75, 95) includes an inner edge (15A, 35A, 55A, 75A, 95A) having a first side (15a, 35a, 55a, 75a, 95a), a second side (15c, 35c, 55c, 75c, 95c), a third side (15b, 35b, 75b, 95b), and a fourth side (15d, 35d, 75d, 95d), the first side (15a, 35a, 55a, 75a, 95a), the second side (15c, 35c, 55c, 75c, 95c), the third side (15b, 35b, 75b, 95b), and the fourth side (15d, 35d, 75d, 95d) forming the shape of the opening (15, 35, 55, 75, 95) in a plane of the side wall through which the opening (15, 35, 55, 75, 95) penetrates, the first side (15a, 35a, 55a, 75a, 95a), forming a lower side, extending along the first surface (7a, 27a, 47a, 67a, 87a) and arranged at a position close to or at the first surface of the bottom base material (7, 27, 47, 67, 87), the second side (15c, 35c, 55c, 75c, 95c), forming an upper side, extending along the first surface (7a, 27a, 47a, 67a, 87a) and arranged at a position farther from the bottom base material (7, 27, 47, 67, 87) than the first side (15a, 35a, 55a, 75a, 95a), the third side (15b, 35b, 75b, 95b) and the fourth side (15d, 35d, 75d, 95d) each connecting the first side (15a, 35a, 55a, 75a, 95a) to the second side (15c, 35c, 55c, 75c, 95c), and the second side (15c, 35c, 55c, 75c, 95c) being longer than the first side (15a, 35a, 55a, 75a, 95a). a bottom base material (7, 27, 47, 67, 87) that includes a first surface (7a, 27a, 47a, 67a, 87a), and a mounting part (12, 32, 52, 72, 92) on the first surface (7a, 27a, 47a, 67a, 87a) on which a light emitting element (3, 23, 43, 63, 83) is to be mounted; and a frame member (9, 29, 49, 69, 89) that includes side walls (9a, 9b, 9c, 9d, 29a, 29b, 29c, 29d, 49a, 49c, 69a, 69b, 69c, 69d, 89a, 89b, 89c, 89d) erected on the first surface (7a, 27a, 47a, 67a, 87a) to surround the mounting part (12, 12a, 32, 52, 72, 92), and an opening (15, 35, 55, 75, 95) that penetrates through one of the side walls (9a, 29a, 49a, 69a, 89a) and is configured to transmit light emitted from the light emitting element (3, 23, 43, 63, 83) to the outside of the light-emitting-element housing member (1, 21, 41, 61, 81, 101A), wherein the opening (15, 35, 55, 75, 95) includes an inner edge (15A, 35A, 55A, 75A, 95A) having a first side (15a, 35a, 55a, 75a, 95a), a second side (15c, 35c, 55c, 75c, 95c), a third side (15b, 35b, 75b, 95b), and a fourth side (15d, 35d, 75d, 95d), the first side (15a, 35a, 55a, 75a, 95a), the second side (15c, 35c, 55c, 75c, 95c), the third side (15b, 35b, 75b, 95b), and the fourth side (15d, 35d, 75d, 95d) forming the shape of the opening (15, 35, 55, 75, 95) in a plane of the side wall through which the opening (15, 35, 55, 75, 95) penetrates, the first side (15a, 35a, 55a, 75a, 95a), forming a lower side, extending along the first surface (7a, 27a, 47a, 67a, 87a) and arranged at a position close to or at the first surface of the bottom base material (7, 27, 47, 67, 87), the second side (15c, 35c, 55c, 75c, 95c), forming an upper side, extending along the first surface (7a, 27a, 47a, 67a, 87a) and arranged at a position farther from the bottom base material (7, 27, 47, 67, 87) than the first side (15a, 35a, 55a, 75a, 95a), the third side (15b, 35b, 75b, 95b) and the fourth side (15d, 35d, 75d, 95d) each connecting the first side (15a, 35a, 55a, 75a, 95a) to the second side (15c, 35c, 55c, 75c, 95c), and the second side (15c, 35c, 55c, 75c, 95c) being longer than the first side (15a, 35a, 55a, 75a, 95a).