The invention provides a ruler for costume design. The ruler comprises a first design ruler, a fastening screw, a second design ruler, a tilt angle sensor, an angle display screen structure, a placement cylinder structure, an insertion groove and a hanging plate structure, wherein the second design ruler is fixed to the rear portion of the first design ruler through the fastening screw, and the tilt angle sensor is installed at the connecting position of the first design ruler and the second design ruler. The ruler has the advantages that the angle at the connecting position of the first design ruler and the second design ruler is more convenient to view by arranging the tilt angle sensor and the angle display screen structure, meanwhile the ruler can be also conveniently used as a protractor, function increase of the ruler for costume design is also promoted, required pens or other articles are more conveniently placed by arranging the placement cylinder structure, meanwhile the functions of the ruler for costume design are also increased, and the hanging plate structure is more convenient to install through arrangement.