PURPOSE: To constitute the string tightener so that it is good style, can execute simply a tightening operation, and also, holds surely a string and is fit for use extending over a long period.

CONSTITUTION: A shape of the inside surface of a case 1 in the string tightener is a trapezoid, and by the inside surfaces of both side walls 3 of the case 1, and pressing parts 14 formed on both side faces of a sliding body 2 for sliding in the case 1, a string is pinched and tightened, and on one of the inside surface of the case 1 or the surface of the sliding body 2, a sliding groove 9 in the longitudinal direction is formed, and on the other, a sliding projecting part 12 fitted into this sliding groove 9 is formed. Also, in the end of the sliding groove 9, an oblique part 10 is formed so that the sliding projecting part 12 is inserted easily, and in the end of the oblique part 10, a control part 11 of the erect surface so that the abovementioned part does not fall out after it is inserted, an operating part 13 is formed before and behind the sliding body 2 and exposed from both opening parts 4, 5 of the case 1, so that the sliding operation can be executed, and the operation for tightening and release is executed.