To provide a method capable of evaluating water quality of pure water by easily and quickly detecting a concentration level of an amine-based organic material or the like included in ultrapure water.

In the method for evaluating the water quality of ultrapure water from the quantity of hydrogen generated by bringing hydrogen-terminated silicon into contact with the ultrapure water, after storing the silicon and the ultrapure water in a container so that a gas phase part is generated on an upper part of the inside of the container, the container is closed, the inside of the container is agitated for a preset predetermined time, a hydrogen concentration of the phase part is measured, and the water quality of the ultrapure water is evaluated from the hydrogen concentration.