In order to provide a mental state measurement system that quantifies a mental state of a worker, a mental state measurement system for analyzing a mental state of a person is configured to have a terminal (TR) to be worn on the person's body. The terminal (TR) is configured to have an acceleration sensor (AC) for measuring the acceleration of motion of the body, a storage unit (STRG) for storing time-series data (SENSD) and a threshold (SF TH) of the acceleration, and a processing unit (ANA) for performing processing (AN03) for determining whether each value (t0804) contained in the time-series data (SENSD) is in a first state (active state) in which the value is equal to or greater than the threshold or in a second state (non-active state) in which the value is less than the threshold, processing (AN04) for determining a duration (L) which is a period of time during which the first state continues, and processing (AN06) for quantifying the mental state of the person on the basis of the duration (L).
