An automatic analysis apparatus comprising: a light source (223; 323; 523; 623; 723; 823; 923) that is adapted to generate light; a fluorescent substance (224; 524) that is excited with the light of the light source (223; 323; 523; 623; 723; 823; 923) to emit light; a condenser lens (229; 529); a reaction cell (208; 508), that is adapted to hold a reaction solution in which a specimen and a reagent are mixed; and a detector that is adapted to detect light transmitted through the reaction cell (208; 508), a first slit (230; 530) and a second slit (231; 531), wherein the light source (223; 323; 523; 623; 723; 823; 923), the fluorescent substance (224; 524), the condenser lens (229; 529), and the slits (230, 231; 530, 531; 849; 949) are provided along a straight line corresponding to an optical axis, the light generated by the light source (223; 323; 523; 623; 723; 823; 923) has a center wavelength equal to or shorter than 340 nm, the first slit (230; 530) is provided between a front focal point (241; 541) of the condenser lens (229; 529) and the fluorescent substance (224; 524), and the second slit (231; 531) is provided between a rear focal point (242; 542) of the condenser lens (229; 529) and the reaction cell (208; 508), the fluorescent substance (224; 524) is adapted to generate light having a wavelength of 340 nm to 800 nm, together with transmitted light from the light source (223; 323; 523; 623; 723; 823; 923), and both the light from the light source (223; 323; 523; 623; 723; 823; 923) and the light from the fluorescent substance (224; 524) enter the reaction cell (208; 508), the widths of the openings (232, 233; 532, 533; 850; 950) of the slits (230, 231; 530, 531; 849; 949) are equal to or narrower than the widths of the rays forming an image of the light source (223; 323; 523; 623; 723; 823; 923) at the respective positions of the first and second slits (230, 231; 530, 531; 849; 949). a light source (223; 323; 523; 623; 723; 823; 923) that is adapted to generate light; a fluorescent substance (224; 524) that is excited with the light of the light source (223; 323; 523; 623; 723; 823; 923) to emit light; a condenser lens (229; 529); a reaction cell (208; 508), that is adapted to hold a reaction solution in which a specimen and a reagent are mixed; and a detector that is adapted to detect light transmitted through the reaction cell (208; 508), a first slit (230; 530) and a second slit (231; 531), wherein the light source (223; 323; 523; 623; 723; 823; 923), the fluorescent substance (224; 524), the condenser lens (229; 529), and the slits (230, 231; 530, 531; 849; 949) are provided along a straight line corresponding to an optical axis, the light generated by the light source (223; 323; 523; 623; 723; 823; 923) has a center wavelength equal to or shorter than 340 nm, the first slit (230; 530) is provided between a front focal point (241; 541) of the condenser lens (229; 529) and the fluorescent substance (224; 524), and the second slit (231; 531) is provided between a rear focal point (242; 542) of the condenser lens (229; 529) and the reaction cell (208; 508), the fluorescent substance (224; 524) is adapted to generate light having a wavelength of 340 nm to 800 nm, together with transmitted light from the light source (223; 323; 523; 623; 723; 823; 923), and both the light from the light source (223; 323; 523; 623; 723; 823; 923) and the light from the fluorescent substance (224; 524) enter the reaction cell (208; 508), the widths of the openings (232, 233; 532, 533; 850; 950) of the slits (230, 231; 530, 531; 849; 949) are equal to or narrower than the widths of the rays forming an image of the light source (223; 323; 523; 623; 723; 823; 923) at the respective positions of the first and second slits (230, 231; 530, 531; 849; 949).