1. An operation guide customizable measuring instrument constructed such that an operation guide for guiding an operation procedure of the instrument is displayable on a display section, and an instrument mechanism for measuring a physical quantity of an object to be measured is operable by an instrument control program equipped with a function which is callable in response to a predetermined command, the instrument comprising: an operation guide storage which variably stores an operation guide file containing the operation guide and the command written in a markup language and a script language therein; an operation guide file processing part which displays the operation guide on the display section based on the operation guide file, and displays an instruction input section for accepting an instruction of an operator on the display section; and a command processing part which outputs the command to the instrument control program so as to call the function corresponding to the command in response to the instruction accepted by the instruction input section.