To solve the problems that pressure detection apparatuses have many restrictions and that it has been required to individually manufacture molds of sheathing cases to result in cost rises.

A sheathing case and a connector part are formed as separate parts. A pressure introduction part is further formed as a separate part. By providing a combined structure using them, it is possible to adapt to various shape requests, adapt to mold manufacture of only parts to be altered even in the case that a new shape is required, and achieve inexpensive and fine adaptation. By providing each part to be combined with a structure to be fitted with each other, it is possible to achieve adaptation without having to raise the number of operation man-hours.