To provide a single hole type permeability test method capable of easily executing permeability tests according to conditions of the ground, variations in water level in the ground, the inner diameter of a test hole, etc. without need to prepare heavy weights of various outer diameters and lengths.

An injection body is thrown into the water in the test hole drilled in the ground. Variations in water level in the test hole are measured with the passage of time by throwing the injection body or lifting it up out of the water. A coefficient of permeability is computed on the basis of information on the differences between measured water levels with the passage of time and the water level of an equilibrium level. A water-absorbing polymer bag 1 acquired by filling a highly-water-absorbing polymer in a bag in which water can permeate is used as the injection body, fastened to a tip of a rope, and thrown in the test hole 5 to make the water-absorbing polymer bag 1 absorb water. Then the rope is speedily lift up the water-absorbing polymer bag 1 into the air out of the water. Variations in water level in the test hole at the time are measured with the passage of time.