A pressure detector disposable inside a tire to detect tire pressure and to transmit the detected tire pressure wirelessly to a controller disposed outside of the tire, the pressure detector comprising: a case provided with a hole portion formed through a bottom surface of the case to allow gas inside the tire to pass through; a circuit board including a sensor having a detection aperture for detecting a gas pressure and mounted on a lower surface of the circuit board facing the bottom surface of the case; characterized by the pressure detector further comprising a plurality of support pillar members standing on the bottom surface of the case and each including a tapered portion at an end of each of the support pillar members, the tapered portion becoming thinner toward the end; the circuit board further including a plurality of mounting holes into which the respective tapered portions of the support pillar members are insertable; and the pressure detector further comprising a packing provided with a through hole that connects an upper surface of the packing to a lower surface of the packing, wherein the case and the circuit board are fixed by a cured resin while the hole portion is connected to the detection aperture via the through hole by inserting the tapered portion of each of the support pillar members into the mounting hole of the circuit board and by sandwiching the packing between the bottom surface of the case and the sensor, and wherein the tapered portion of each of the support pillar members includes: a base having an outer diameter larger than an inner diameter of each of the mounting holes; and a leading end having an outer diameter smaller than the inner diameter of each of the mounting holes. a case provided with a hole portion formed through a bottom surface of the case to allow gas inside the tire to pass through; a circuit board including a sensor having a detection aperture for detecting a gas pressure and mounted on a lower surface of the circuit board facing the bottom surface of the case; characterized by the pressure detector further comprising a plurality of support pillar members standing on the bottom surface of the case and each including a tapered portion at an end of each of the support pillar members, the tapered portion becoming thinner toward the end; the circuit board further including a plurality of mounting holes into which the respective tapered portions of the support pillar members are insertable; and the pressure detector further comprising a packing provided with a through hole that connects an upper surface of the packing to a lower surface of the packing, wherein the case and the circuit board are fixed by a cured resin while the hole portion is connected to the detection aperture via the through hole by inserting the tapered portion of each of the support pillar members into the mounting hole of the circuit board and by sandwiching the packing between the bottom surface of the case and the sensor, and wherein the tapered portion of each of the support pillar members includes: a base having an outer diameter larger than an inner diameter of each of the mounting holes; and a leading end having an outer diameter smaller than the inner diameter of each of the mounting holes.