A water absorbent resin powder comprising a polyacrylic acid (salt)-based water absorbent resin as a main component, the water absorbent resin powder satisfying: the water absorbent resin powder having a saline flow conductivity of not less than 10 [x 10 -7 ·cm 3 ·s·g -1], as measured in accordance with the SFC test method described in the description; characterized in that the water absorbent resin powder satisfies and: the water absorbent resin powder containing particles smaller than 150 μm in a ratio of 0 mass% to 4.5 mass% before an impact resistance test, and the water absorbent resin powder containing, in a ratio of 0 mass% to 4.5 mass%, particles smaller than 150 μm after the impact resistance test, as measured in accordance with method (i) as defined in the description; and the water absorbent resin powder having a thermal conductivity of not more than 125 [mW/(m·K)], as measured in accordance with method (ii) as defined in the description. A water absorbent resin powder comprising a polyacrylic acid (salt)-based water absorbent resin as a main component, the water absorbent resin powder satisfying: the water absorbent resin powder having a saline flow conductivity of not less than 10 [x 10 -7 ·cm 3 ·s·g -1], as measured in accordance with the SFC test method described in the description; characterized in that the water absorbent resin powder satisfies and: the water absorbent resin powder containing particles smaller than 150 μm in a ratio of 0 mass% to 4.5 mass% before an impact resistance test, and the water absorbent resin powder containing, in a ratio of 0 mass% to 4.5 mass%, particles smaller than 150 μm after the impact resistance test, as measured in accordance with method (i) as defined in the description; and the water absorbent resin powder having a thermal conductivity of not more than 125 [mW/(m·K)], as measured in accordance with method (ii) as defined in the description. the water absorbent resin powder having a saline flow conductivity of not less than 10 [x 10 -7 ·cm 3 ·s·g -1], as measured in accordance with the SFC test method described in the description; characterized in that the water absorbent resin powder satisfies and: the water absorbent resin powder containing particles smaller than 150 μm in a ratio of 0 mass% to 4.5 mass% before an impact resistance test, and the water absorbent resin powder containing, in a ratio of 0 mass% to 4.5 mass%, particles smaller than 150 μm after the impact resistance test, as measured in accordance with method (i) as defined in the description; and the water absorbent resin powder having a thermal conductivity of not more than 125 [mW/(m·K)], as measured in accordance with method (ii) as defined in the description. the water absorbent resin powder containing particles smaller than 150 μm in a ratio of 0 mass% to 4.5 mass% before an impact resistance test, and the water absorbent resin powder containing, in a ratio of 0 mass% to 4.5 mass%, particles smaller than 150 μm after the impact resistance test, as measured in accordance with method (i) as defined in the description; and the water absorbent resin powder having a thermal conductivity of not more than 125 [mW/(m·K)], as measured in accordance with method (ii) as defined in the description.