A pressure detecting apparatus includes: a housing (11) for forming fluid chambers (21A and 21B) into which external fluid pressures are imported respectively; a pressure-receiving member (31) slidably provided in the housing (11) for receiving the fluid pressures from the fluid chambers (21A and 21B); an elastic member (35) supported by the housing (11) and elastically deformed due to a slide displacement of the pressure-receiving member (31) from a predetermined position; a displacement detecting means (12) for detecting the displacement of the pressure-receiving member (31) from the predetermined position; the elastic member including a base portion supported by the housing, an engagement portion engaged with the pressure-receiving member, and a flexible arm extending from the base portion toward the engagement portion along a plane approximately perpendicular to a direction of sliding of the pressure-receiving member.