To provide a pressure receiving part capable of taking a large displacement even at a low pressure by forming a pre-loaded diaphragm in a wave shape.

This transmitter comprises a high pressure side diaphragm part having a high pressure side process diagram and a high pressure side pre-loaded diaphragm, a filled high pressure side transmission oil, a low pressure side diaphragm part having a low pressure side process diagram and a low pressure side pre-loaded diaphragm, a filled low pressure side transmission oil, and a differential pressure sensor part detecting a pressure difference between the high pressure side transmission oil and the low pressure side transmission oil. The high pressure side and/or the low pressure side pre-loaded diaphragm comprises a center flat part formed in a disk shape at the center position thereof, a wave part in which the outer side of the center flat part is formed in a wave shape so as to be extended to the surface thereof in contact with the high pressure side and low pressure side liquid-contact surface, and an outer flat part formed by flattening the wave part ranging from the outside to the outer peripheral end part thereof.