A water quality analyzer comprising: a sample cell configured to comprise sample water to be measured; an excitation light irradiating optical system configured to irradiate the sample water to be measured with first light source light for excitation along its optical axis; a fluorescence detecting optical system configured and positioned to detect fluorescence emitted from a specific component in the sample water along its optical axis, the fluorescence excited by the irradiation with the first light source light for excitation; a scattered light irradiating optical system configured to irradiate the sample water with second light source light along its optical axis for scattered light detection; a scattered light detecting optical system configured and positioned to detect scattered light along its optical axis, the scattered light scattered by microparticles in the sample water by the irradiation with the second light source light for scattered light detection, wherein the fluorescence detecting optical system is configured and positioned to detect an amount of the light emitted from the scattered light irradiating optical system, and the scattered light detecting optical system is configured and positioned to detect an amount of the light emitted from the excitation light irradiating optical system, wherein the excitation light irradiating optical system and the scattered light detecting optical system are arranged so as to be opposed to each other across the sample cell, and the scattered light irradiating optical system and the fluorescence detecting optical system are arranged so as to be opposed to each other across the sample cell, wherein the optical axis of the excitation light irradiating optical system and the optical axis of the fluorescence detecting optical system cross at a first intersection point, and the optical axis of the scattered light irradiating optical system and the optical axis of the scattered light detecting optical system cross at a second intersection point, characterized in that the first and the second intersection points (P1; P2) are arranged in the sample cell with a distance, the distance being the distance between the first intersection point and the second intersection point, and in that a first plane formed by the optical axis of the excitation light irradiating optical system and the optical axis of the fluorescence detecting optical system and a second plane formed by the optical axis of the scattered light irradiating optical system and the optical axis of the scattered light detecting optical system are configured to be arranged in the sample cell with the distance mutually. a sample cell configured to comprise sample water to be measured; an excitation light irradiating optical system configured to irradiate the sample water to be measured with first light source light for excitation along its optical axis; a fluorescence detecting optical system configured and positioned to detect fluorescence emitted from a specific component in the sample water along its optical axis, the fluorescence excited by the irradiation with the first light source light for excitation; a scattered light irradiating optical system configured to irradiate the sample water with second light source light along its optical axis for scattered light detection; a scattered light detecting optical system configured and positioned to detect scattered light along its optical axis, the scattered light scattered by microparticles in the sample water by the irradiation with the second light source light for scattered light detection, wherein the fluorescence detecting optical system is configured and positioned to detect an amount of the light emitted from the scattered light irradiating optical system, and the scattered light detecting optical system is configured and positioned to detect an amount of the light emitted from the excitation light irradiating optical system, wherein the excitation light irradiating optical system and the scattered light detecting optical system are arranged so as to be opposed to each other across the sample cell, and the scattered light irradiating optical system and the fluorescence detecting optical system are arranged so as to be opposed to each other across the sample cell, wherein the optical axis of the excitation light irradiating optical system and the optical axis of the fluorescence detecting optical system cross at a first intersection point, and the optical axis of the scattered light irradiating optical system and the optical axis of the scattered light detecting optical system cross at a second intersection point, characterized in that the first and the second intersection points (P1; P2) are arranged in the sample cell with a distance, the distance being the distance between the first intersection point and the second intersection point, and in that a first plane formed by the optical axis of the excitation light irradiating optical system and the optical axis of the fluorescence detecting optical system and a second plane formed by the optical axis of the scattered light irradiating optical system and the optical axis of the scattered light detecting optical system are configured to be arranged in the sample cell with the distance mutually.