Abstract: A partitioning portion partitions a fuel chamber into a first space, which receives a pressurizing chamber forming portion and is communicated with an inflow pipe, and a second space, which is communicated with an outflow pipe. A flow passage forming portion extends from the partitioning portion toward the first space side and forms a communicating flow passage, which communicates between the first space and the second space. Thereby, vapor contained in the fuel, which is returned from a pressurizing chamber to the fuel chamber, is accumulated as bubbles in the first space, which receives the pressurizing chamber forming portion. The first space is communicated with the outside through the communicating flow passage and the second space. Therefore, outputting of air bubbles of the first space to the outside can be effectively limited in comparison to a case where the fuel chamber is directly communicated with the outside.