A polycrystalline diamond sintered material tool comprising: a cemented carbide substrate, which is mainly composed of WC and includes Co; and a diamond layer containing a metal catalyst made of Co provided on the cemented carbide substrate which contains 9-18% by mass of Co, wherein an average layer thickness of a Co rich layer formed in an interface between the cemented carbide substrate and the diamond layer is 30 μm or less, the Co rich layer being a region from the interface between the diamond layer and the WC-based cemented carbide to the diamond layer and having a Co content of 1.1×C DIA or more, wherein C DIA is defined as an average content of Co included in the diamond layer, a value of D/D O is less than 2 when D is defined as average grain size of WC particles in a region from the interface between the cemented carbide substrate and the diamond layer to 50 μm toward an inside of the diamond layer; and D O is defined as an average grain size of WC particles in the inside of the cemented carbide substrate, the average layer thickness is obtained by measuring the Co contents from the interface between the cemented carbide substrate and the diamond layer toward each of inside directions of the cemented carbide substrate and the diamond layer in the distance of 50μm each, and the average grain size of WC particles is measured by image processing of scanning electron microscope photograph observed at 500 times to 3000 times and averaging the measured values at these multiple points, wherein a value of C MAX /C DIA is 2 or less when C MAX is defined as a peak value of a Co content in the Co rich layer, and wherein the values of C MAX and C DIA are obtained by line analysis with an Electron Probe MicroAnalyzer by scanning the distance of 100μm from the diamond layer toward the cemented carbide substrate with a 20μm of the beam diameter and 0.5μm of the measurement interval, detecting the characteristic X-ray of Co generated by the accelerated electron beam radiated from the Electron Probe MicroAnalyzer; and obtaining the Co contents as the count numbers in counts per second at each position, and the value of C DIA is defined as the average values measured at least at 200 different points with 0.5 μm measurement intervals in the layer direction of the diamond layer from the point beyond the Co rich layer to the diamond layer side. an average layer thickness of a Co rich layer formed in an interface between the cemented carbide substrate and the diamond layer is 30 μm or less, the Co rich layer being a region from the interface between the diamond layer and the WC-based cemented carbide to the diamond layer and having a Co content of 1.1×C DIA or more, wherein C DIA is defined as an average content of Co included in the diamond layer, a value of D/D O is less than 2 when D is defined as average grain size of WC particles in a region from the interface between the cemented carbide substrate and the diamond layer to 50 μm toward an inside of the diamond layer; and D O is defined as an average grain size of WC particles in the inside of the cemented carbide substrate, the average layer thickness is obtained by measuring the Co contents from the interface between the cemented carbide substrate and the diamond layer toward each of inside directions of the cemented carbide substrate and the diamond layer in the distance of 50μm each, and the average grain size of WC particles is measured by image processing of scanning electron microscope photograph observed at 500 times to 3000 times and averaging the measured values at these multiple points, wherein a value of C MAX /C DIA is 2 or less when C MAX is defined as a peak value of a Co content in the Co rich layer, and wherein the values of C MAX and C DIA are obtained by line analysis with an Electron Probe MicroAnalyzer by scanning the distance of 100μm from the diamond layer toward the cemented carbide substrate with a 20μm of the beam diameter and 0.5μm of the measurement interval, detecting the characteristic X-ray of Co generated by the accelerated electron beam radiated from the Electron Probe MicroAnalyzer; and obtaining the Co contents as the count numbers in counts per second at each position, and the value of C DIA is defined as the average values measured at least at 200 different points with 0.5 μm measurement intervals in the layer direction of the diamond layer from the point beyond the Co rich layer to the diamond layer side.