A measuring probe comprising: a stylus(336, 436) having a contact part(362, 462) to be brought into contact with an object to be measured; a probe housing capable of supporting the stylus(336, 436) on an axial center; detection elements (325, 425) capable of detecting a movement of the contact part(362, 462); a signal processing circuit (320, 420) that processes outputs of the detection elements(325, 425); and a plurality of supporting members (322, 324, 422, 424) disposed in an axial direction of the probe housing, the supporting members (322, 324, 422, 424) having a rotationally symmetric shape and allowing for an attitude change of the stylus (336, 436), wherein four said detection elements(325, 425) are disposed at fourfold symmetric positions in at least one of the plurality of supporting members (322, 324, 422, 424) that includes a deformable arm part, and the signal processing circuit(320, 420) includes a first processing part(364, 464) that processes the outputs of the detection elements(325, 425) to output three displacement signals(Vx, Vy, Vz) representing displacement components of the contact part (362, 462) in mutually perpendicular three directions, respectively, wherein the signal processing circuit (320, 420) further includes: a second processing part(366, 466) that outputs a composite signal(Vout) obtained by combining the three displacement signals (Vx, Vy, Vz); and a comparison part (378, 478) that compares a signal level of the composite signal (Vout) with a predetermined reference value(Vs), and the signal processing circuit(320, 420) outputs a touch signal (Sout) when the signal level of the composite signal (Vout) is higher than or equal to the predetermined reference value (Vs), wherein the first processing part(364, 464) includes: a first addition part that adds all of four outputs from the four detection elements(325, 425); and subtraction parts(364X, 364Y) that subtract, from outputs of two of the detection elements (325, 425) at positions different from each other by an angle of 90 degrees around the axial center, outputs of the detection elements (325, 425) at positions different from the two of the detection elements (325, 425) by an angle of 180 degrees, respectively, and the second processing part(366, 466) includes: squaring parts(370X, 370Y, 370Z) that square the three displacement signals(Vx, Vy, Vz, Vax, Vay, Vaz), respectively; and a second addition part that adds all of squared signals (Vsx, Vsy, Vsz) outputted from the squaring parts(370X, 370Y, 370Z). a stylus(336, 436) having a contact part(362, 462) to be brought into contact with an object to be measured; a probe housing capable of supporting the stylus(336, 436) on an axial center; detection elements (325, 425) capable of detecting a movement of the contact part(362, 462); a signal processing circuit (320, 420) that processes outputs of the detection elements(325, 425); and a plurality of supporting members (322, 324, 422, 424) disposed in an axial direction of the probe housing, the supporting members (322, 324, 422, 424) having a rotationally symmetric shape and allowing for an attitude change of the stylus (336, 436), wherein four said detection elements(325, 425) are disposed at fourfold symmetric positions in at least one of the plurality of supporting members (322, 324, 422, 424) that includes a deformable arm part, and the signal processing circuit(320, 420) includes a first processing part(364, 464) that processes the outputs of the detection elements(325, 425) to output three displacement signals(Vx, Vy, Vz) representing displacement components of the contact part (362, 462) in mutually perpendicular three directions, respectively, wherein the signal processing circuit (320, 420) further includes: a second processing part(366, 466) that outputs a composite signal(Vout) obtained by combining the three displacement signals (Vx, Vy, Vz); and a comparison part (378, 478) that compares a signal level of the composite signal (Vout) with a predetermined reference value(Vs), and the signal processing circuit(320, 420) outputs a touch signal (Sout) when the signal level of the composite signal (Vout) is higher than or equal to the predetermined reference value (Vs), wherein the first processing part(364, 464) includes: a first addition part that adds all of four outputs from the four detection elements(325, 425); and subtraction parts(364X, 364Y) that subtract, from outputs of two of the detection elements (325, 425) at positions different from each other by an angle of 90 degrees around the axial center, outputs of the detection elements (325, 425) at positions different from the two of the detection elements (325, 425) by an angle of 180 degrees, respectively, and the second processing part(366, 466) includes: squaring parts(370X, 370Y, 370Z) that square the three displacement signals(Vx, Vy, Vz, Vax, Vay, Vaz), respectively; and a second addition part that adds all of squared signals (Vsx, Vsy, Vsz) outputted from the squaring parts(370X, 370Y, 370Z).