A light source apparatus comprising: a light source that outputs excitation light (E1, E2, E3); a first wavelength converter that contains a first phosphor and converts the excitation light into first fluorescence (KY1, KB) having a first wavelength band different from a wavelength band of the excitation light; a second wavelength converter that contains a second phosphor and converts the excitation light into second fluorescence (KY2, KR) having a second wavelength band different from the wavelength band of the excitation light; and a light guide that guides the second fluorescence having exited out of the second wavelength converter to the first wavelength converter , wherein the first wavelength converter has a first end surface and a second end surface that face each other and a first side surface (51c3, 51c4; 71c3, 71c4) that intersects the first and second end surfaces (51a, 71a; 51b, 71b), the second wavelength converter has a third end surface and a fourth end surface that face each other and a second side surface (52c1, 52c2, 52c3, 52c4; 72c1) that intersects the third and fourth end surfaces (52a, 72a; 52b, 72b), the first side surface (51c3, 51c4; 71c3, 71c4) of the first wavelength converter faces the second side surface (52c1, 52c2, 52c3, 52c4; 72c1) of the second wavelength converter , the light guide has a reflection surface (43f1, 44f2; 46f, 55f) that faces the third end surface of the second wavelength converter and the second end surface of the first wavelength converter , and the first fluorescence and the second fluorescence exit via the first end surface of the first wavelength converter . a light source that outputs excitation light (E1, E2, E3); a first wavelength converter that contains a first phosphor and converts the excitation light into first fluorescence (KY1, KB) having a first wavelength band different from a wavelength band of the excitation light; a second wavelength converter that contains a second phosphor and converts the excitation light into second fluorescence (KY2, KR) having a second wavelength band different from the wavelength band of the excitation light; and a light guide that guides the second fluorescence having exited out of the second wavelength converter to the first wavelength converter , wherein the first wavelength converter has a first end surface and a second end surface that face each other and a first side surface (51c3, 51c4; 71c3, 71c4) that intersects the first and second end surfaces (51a, 71a; 51b, 71b), the second wavelength converter has a third end surface and a fourth end surface that face each other and a second side surface (52c1, 52c2, 52c3, 52c4; 72c1) that intersects the third and fourth end surfaces (52a, 72a; 52b, 72b), the first side surface (51c3, 51c4; 71c3, 71c4) of the first wavelength converter faces the second side surface (52c1, 52c2, 52c3, 52c4; 72c1) of the second wavelength converter , the light guide has a reflection surface (43f1, 44f2; 46f, 55f) that faces the third end surface of the second wavelength converter and the second end surface of the first wavelength converter , and the first fluorescence and the second fluorescence exit via the first end surface of the first wavelength converter . <EOS>