To provide a semiconductor process monitoring method which can measure film thickness or the like of a film formed on a semiconductor substrate readily and stably in a nondestructive manner, and a semiconductor process monitoring device having durability.

In a semiconductor process monitoring method for carrying out thickness processing of a semiconductor substrate by using wet etching, relationship between electrical characteristics regarding process liquid 3 in wet etching process and the thickness or thickness variation amount of a semiconductor substrate 7, which is a processing object, is obtained in advance by using a high frequency power supply 4 which applies high frequency voltage or high frequency power. When the semiconductor substrate 7 is subjected to wet etching process, electrical characteristics of the process liquid 3 in wet etching process are measured and the thickness variation amount or thickness amount of the semiconductor substrate 7 is calculated based on the relationship. When the thickness of the semiconductor substrate 7 is a desired thickness, wet etching process is finished.