Abstract: A light emitting device is composed of a light source, including a plurality of LEDs, and a polarizing element that receives rays of light emitted from the light source and causes at least in part the rays of light to transmit therethrough and be then incident on a work. Besides, each of the plurality of LEDs has an optical axis tilting at a first angle ?1 with respect to the work, whereas a second angle ?2, defined as half of a light distribution angle of the rays of light emitted from each of the plurality of LEDs, is set to be less than the first angle ?1. Moreover, an illuminance and a cumulative illuminance of the rays of light incident on the work or an exposure surface are adjusted by changing electricity to be inputted to the plurality of LEDs.