To provide a penetration rod capable of determining an accurate soil property by measuring the true resistivity of the ground at each underground depth, and by evaluating soil quality based on each measured value.

The penetration rod 1 has a rod body 2 penetrating underground, and the rod body 2 is attached with ground resistivity measuring means 6a, 6b, 6c, 6d for measuring the resistivity of the ground, and clearance water resistivity measuring means 7a, 7b, 7c, 7d for measuring the resistivity of ground clearance water. By this, true resistivity in the consideration of each resistivity of clearance water which is peculiar to the ground can be acquired at each depth, and a ground property and the soil quality can be evaluated accurately and multilaterally.