A surface texture measuring device, comprising: a contact piece having a tip capable of contacting with a measuring target; and an arithmetic means operative to compute on the basis of measurement point sequences obtained by the contact piece, whereby the arithmetic means comprises: first pseudo measurement point sequence obtaining means operative to drive the contact piece such that the contact piece traces a surface of a reference workpiece (4A, 4B) having a reference shape, and obtain a locus of a certain position of the contact piece as a first pseudo measurement point sequence (P1i); contact piece model calculating means operative to calculate, based on the first pseudo measurement point sequence (P1i) and a design surface specifying the surface of the reference workpiece (4A, 4B), a contact piece model representing a surface shape of the contact piece and placed in a pseudo space; second pseudo measurement point sequence obtaining means operative to place the contact piece model such that a surface of the contact piece model contacts with a reference surface specifying a measuring surface of the measuring target and that the contact piece model takes a same posture as that taken by the contact piece during a measurement, and calculate a reference position of the contact piece model as a second pseudo measurement point sequence (P2i); and replacement determination means operative to determine whether or not to replace the contact piece based on the second pseudo measurement point sequence (P2i). a contact piece having a tip capable of contacting with a measuring target; and an arithmetic means operative to compute on the basis of measurement point sequences obtained by the contact piece, whereby the arithmetic means comprises: first pseudo measurement point sequence obtaining means operative to drive the contact piece such that the contact piece traces a surface of a reference workpiece (4A, 4B) having a reference shape, and obtain a locus of a certain position of the contact piece as a first pseudo measurement point sequence (P1i); contact piece model calculating means operative to calculate, based on the first pseudo measurement point sequence (P1i) and a design surface specifying the surface of the reference workpiece (4A, 4B), a contact piece model representing a surface shape of the contact piece and placed in a pseudo space; second pseudo measurement point sequence obtaining means operative to place the contact piece model such that a surface of the contact piece model contacts with a reference surface specifying a measuring surface of the measuring target and that the contact piece model takes a same posture as that taken by the contact piece during a measurement, and calculate a reference position of the contact piece model as a second pseudo measurement point sequence (P2i); and replacement determination means operative to determine whether or not to replace the contact piece based on the second pseudo measurement point sequence (P2i). first pseudo measurement point sequence obtaining means operative to drive the contact piece such that the contact piece traces a surface of a reference workpiece (4A, 4B) having a reference shape, and obtain a locus of a certain position of the contact piece as a first pseudo measurement point sequence (P1i); contact piece model calculating means operative to calculate, based on the first pseudo measurement point sequence (P1i) and a design surface specifying the surface of the reference workpiece (4A, 4B), a contact piece model representing a surface shape of the contact piece and placed in a pseudo space; second pseudo measurement point sequence obtaining means operative to place the contact piece model such that a surface of the contact piece model contacts with a reference surface specifying a measuring surface of the measuring target and that the contact piece model takes a same posture as that taken by the contact piece during a measurement, and calculate a reference position of the contact piece model as a second pseudo measurement point sequence (P2i); and replacement determination means operative to determine whether or not to replace the contact piece based on the second pseudo measurement point sequence (P2i).