The invention provides a germanium photodetector in which a dark current is reduced without loss of a photocurrent. This invention is provided with: a silicon substrate; a lower cladding layer formedon the silicon substrate; a core layer (210) formed on the lower cladding layer; a p-type silicon slab (211) formed on a part of the core layer (210) and doped with p-type impurity ions; p++ silicon electrode parts (212, 213) doped with a p-type impurity in a high concentration, the p++ silicon electrode parts (212, 213) acting as electrodes; and germanium layers (241, 242) for absorbing light. The invention is further provided with an upper cladding layer, an n-type germanium region of the upper part of the germanium layers that has been doped with an n-type impurity, and an electrode. In theinvention, by having two germanium layers (241, 242) provided on the p-type silicon slab (211), the area over which each of the germanium layers is in contact with the p-type silicon slab (211) is reduced, which makes it possible to reduce the dark current caused by threading dislocation.