A detection method for causing a computer to execute processing includes acquiring image information obtained by imaging a subject in a moving body, acquiring illuminance information that indicates an illuminance in the moving body, generating first feature information regarding a time-series change in a pupil diameter of the subject on the basis of the acquired image information, generating second feature information regarding a time-series change in the illuminance in the moving body on the basis of the acquired illuminance information, generating reaction information regarding a reflection speed of a pupil of the subject with respect to light emitted to the subject on the basis of the generated first and second feature information, and detecting a fatigue state of the subject on the basis of the generated reaction information.
