An attachment structure for a pressure detector that is such that the pressure detector is attached in an airtight manner within an insertion hole of an attachment tool main body attached to a mechanical device or pipelines, with a pipe, a gasket presser, a gasket, a split ring, and a bonnet. The configuration is such that the gasket presser and the split ring are inserted into the insertion hole of the attachment tool main body, the bonnet is inserted into the insertion hole, the bonnet is fastened to the attachment tool main body side, the gasket presser and the gasket are pressed by the split ring, and sealing portions are formed between the bottom surface of the insertion hole and one end surface of the gasket and between the tip end surface of the gasket restraint and the other end surface of the gasket.