<p>In a sliding door apparatus, a first lower frame is disposed on a lower portion of a first doorway, and a second lower frame is disposed on a lower portion of a second doorway. A light emitter that illuminates an illuminated surface that is a surface of the second lower frame that faces the first lower frame is disposed on a first portion of either an upper portion or a lower portion of the first doorway. A light receiver that receives light that is emitted from the light emitter and reflected by the illuminated surface is disposed on a second portion of the upper portion or the lower portion of the first doorway. A determination controlling portion determines presence or absence of an obstruction by detecting whether or not the light that is emitted from the light emitter and reflected by the illuminated surface is received by the light receiver.</p>
