A waveguide photodetector includes a first contact layer of a first conductivity type, a waveguide layer, and a second contact layer of a second conductivity type that are sequentially formed on the semiconductor substrate. The waveguide layer includes a first cladding layer of the first conductivity type disposed on a side of the first contact layer, a second cladding layer of the second conductivity type disposed on a side of the second contact layer, and the core layer disposed between the first cladding layer and the second cladding layer. The core layer includes a light absorption layer and an impurity-doped light absorption layer that has a higher concentration of a p-type impurity than that of the light absorption layer and is disposed on a side of a light incident face.