A method of fabricating a surface emitting semiconductor laser includes the following steps. A first laminate of semiconductor layers and a second laminate of semiconductor layers are formed on a substrate. The first laminate includes a first reflection mirror layer of a first conduction type, an active region, a III-V semiconductor layer containing Al, and a second reflection mirror layer of a second conduction type, the second laminate being used for monitoring and having an oxidizable region. The first and second laminates are etched so as to form mesas on the substrate in which side surface of the III-V semiconductor layer contained in the first laminate is exposed. Oxidization of the III-V semiconductor layer from the side surface is started at an oxidization rate. During oxidization, a reflectance of the second laminate for monitoring or its variation is monitored, and oxidization of the III-V semiconductor layer is terminated after a constant time from a time when the reflectance or its variation reaches a corresponding given value.