A portable terminal device (1) capable of easily evaluating mental fatigue
comprises: an operation unit (4); an imaging unit for measuring ambient
light (5); a display screen (2) or a light-emitting element (3) for
presenting a flashing image or light while a flicker frequency of the
flashing source is being monotonically changed from a start frequency to
an ending frequency; and a recording unit for, when a user operates the
operation unit (4) as the user perceives a flicker, recording the flicker
frequency at the time point as a measured frequency, wherein: a first
frequency datum, which is the measured frequency measured when the user
is in a healthy condition, is associated with a first luminance datum,
which is a measured ambient luminance, and the associated datum is stored
in the recording unit, a proportion of decrease of a second frequency
datum, which is the measured frequency measured when the user is not in a
healthy condition, from the first frequency datum recorded in the
recording unit and associated with the first luminance datum which has
the same or similar order of magnitude to a second luminance datum, which
is a measured ambient luminance, is calculated to evaluate a degree of
fatigue of the user.