A light source apparatus (2, 22, 23, 24) comprising: a light source (35, 36, 37, 38) that outputs excitation light (E1, E2, E3); a first wavelength converter (51, 71) 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 (52, 72) 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 (42, 46, 55, 67) that guides the second fluorescence having exited out of the second wavelength converter (52, 72) to the first wavelength converter (51, 71), wherein the first wavelength converter (51, 71) has a first end surface (51a, 71a) and a second end surface (51b, 71b) 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 (52, 72) has a third end surface (52a, 72a) and a fourth end surface (52b, 72b) 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 (51, 71) faces the second side surface (52c1, 52c2, 52c3, 52c4; 72c1) of the second wavelength converter (52, 72), the light guide (42, 46, 55, 67) has a reflection surface (43f1, 44f2; 46f, 55f) that faces the third end surface (52a, 72a) of the second wavelength converter (52, 72) and the second end surface (51b, 71b) of the first wavelength converter (51, 71), and the first fluorescence and the second fluorescence exit via the first end surface (51a, 71a) of the first wavelength converter (51, 71). a light source (35, 36, 37, 38) that outputs excitation light (E1, E2, E3); a first wavelength converter (51, 71) 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 (52, 72) 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 (42, 46, 55, 67) that guides the second fluorescence having exited out of the second wavelength converter (52, 72) to the first wavelength converter (51, 71), wherein the first wavelength converter (51, 71) has a first end surface (51a, 71a) and a second end surface (51b, 71b) 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 (52, 72) has a third end surface (52a, 72a) and a fourth end surface (52b, 72b) 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 (51, 71) faces the second side surface (52c1, 52c2, 52c3, 52c4; 72c1) of the second wavelength converter (52, 72), the light guide (42, 46, 55, 67) has a reflection surface (43f1, 44f2; 46f, 55f) that faces the third end surface (52a, 72a) of the second wavelength converter (52, 72) and the second end surface (51b, 71b) of the first wavelength converter (51, 71), and the first fluorescence and the second fluorescence exit via the first end surface (51a, 71a) of the first wavelength converter (51, 71).