To homogenize radiation angles of two kinds of lights and to efficiently use the lights while restricting an increase in manufacture cost when multiplexing a white illumination light and a narrowband light.A light source apparatus according to the present disclosure includes a white illumination light source configured to emit a white illumination light, one or more narrowband light sources configured to emit a narrowband light, a multiplexing optical system configured to multiplex the white illumination light and the narrowband light, a condensing optical system configured to couple the multiplexed white illumination light and narrowband light to a light guide provided in an image acquisition apparatus and configured to guide an illumination light into the image acquisition apparatus, and a light amount distribution adjustment device provided on an optical axis between the narrowband light source and the multiplexing optical system and configured to adjust a light amount distribution of the narrowband light, in which the light guide is a bundle-type light guide in which multimode optical fibers are bundled or a liquid light guide filling a liquid therein, and the light amount distribution adjustment device adjusts a light amount distribution of the narrowband light such that a radiation angle distribution of the narrowband light transmitting through the light amount distribution adjustment device is anisotropic.
