A biological information measuring device according to an aspect of the present disclosure includes: a light source that, in operation, emits irradiation light for irradiating a test portion of a subject； a light detector that, in operation, detects light from the subject and outputs an electrical signal corresponding to the light； and a control circuit that, in operation, determines a power of the irradiation light emitted by the light source, and that, in operation, measures biological information related to a blood flow at the test portion based on the electrical signal. The control circuit, in operation, detects a distance between the light source and the test portion based on the electrical signal, and determines the power of the irradiation light such that the power of the irradiation light is increased as the distance increases.
