PURPOSE: To judge which sewing characteric is commercially most permittable by guide-feeding a test piece of fabric by means of a selected traveling speed in a prescribed traveling route as against a sewing machine needle, forming stitches through the use of a specified type sewing thread, simulating normal states in an automatic sewing work and testing the sewing characteristics of the various types of sewing threads.

CONSTITUTION: The states where the fabric in case of sewing a pocket on an automatic pocket setter is moved is respective directions as against the needle are simulated by changing angle relation between the adjacent leg parts of zigzag sewing lines concerning the reciprocative movement speed of a guide board 62 and the speed drawing a fabric piece in the lower part of the needle 42. When the test piece of fabric is moved forward or sideward as against the needle 42, various kinds of stress is added to the needle in case the sewing needle 42 penetrates the fabric, sewing is executed while the fabric is moved in the various kinds of directions and various kinds of defect occur in case of the usage of different types of sewing threads so that recognition and judgement are economically and quickly enabled.