A length measuring instrument for measuring length with a measure includes: a measure on which a code is printed, a plurality of patterns each allotted to a different number being arranged, each of the patterns having digits to which an N-notation number (N being 3 or greater) is allotted, each of the digits having a different color corresponding to the allotted numerical value, the patterns being arranged in ascending order or descending order, a Hamming distance between patterns adjacent to each other in an array direction being 1, an amount of change in numerical value at the same digit between the adjacent patterns being 1 in the code; a reading unit that optically reads patterns printed on the measure; and a measuring unit that measures a length of a measurement target from a result of the reading by the reading unit.