A light source apparatus includes a laser light source configured to emit laser light to illuminate an object, a light receiving section configured to output a light detection signal corresponding to a light quantity of at least part of the received laser light emitted from the laser light source, a calculation processing section configured to output either a calculated value obtained by integrating, for a predetermined time period, values resulting from multiplying detection values of the light detection signals by a correction coefficient or a calculated value obtained by multiplying values resulting from integrating, for a predetermined time period, detection values of the light detection signals by a correction coefficient, a determining section configured to determine whether or not the calculated value is equal to or less than a threshold, a light source control section configured to control the laser light source based on the determination result obtained by the determining section, and an adjustment coefficient calculating section configured to calculate an adjustment coefficient for adjusting the correction coefficient in response to a change in loss produced in an optical transmission line along which the laser light emitted from the laser light source is emitted to the object.
