Wavelength conversion element, light source device, and projector

A wavelength conversion element comprising:

• a wavelength conversion layer including a light-incident surface;
• a light-transmissive member provided on the light-incident surface side of the wavelength conversion layer and including a support surface including an inclined portion inclined with respect to the light-incident surface;
• and
• a first reflection portion provided along the support surface and reflecting fluorescence light emitted from the wavelength conversion layer, wherein
• at least a portion of the first reflection portion is formed of a dichroic film that transmits excitation light for exciting the wavelength conversion layer,
• the light-transmissive member is disposed such that the excitation light passes through the dichroic film and the light-incident surface in this order to enter the wavelength conversion layer, and
• when a plane including the light-incident surface is defined as a reference surface and a gap between the reference surface and the first reflection portion in a direction perpendicular to the reference surface is defined as a distance between the reference surface and the first reflection portion, the inclined portion is inclined with respect to the light-incident surface such that a distance between the reference surface and the first reflection portion in a periphery region of the first reflection portion is smaller than a distance between the reference surface and the first reflection portion in a central region of the first reflection portion.