PURPOSE: To make it possible to automatically balance the stitch and tense the thread in any movement of feeding by providing a timing-deciding device by which work- feeding is partially done while a needle thread is released by both of contact members after an output from a phase-detecting device for an arm shaft and a stitch-pattern data from a storing device are received, and the larger the feeding movement of work is, the later the starting timing of a period of the needle thread being released is made.

CONSTITUTION: A timing-deciding device is operated by a phase signal from a phase- detecting device and a stitch-pattern data from a storing device, and work-feeding is partially done while a needle thread is released by a pair of contact members. The starting timing of a period of the needle thread being released is also so decided that the larger the feeding movement of work is, the later the time of the needle thread being released is made. Since a controlling device controls a contact member- driving device so that the needle thread can be released by its starting timing, the needle thread is released after both of the contact members are relatively shifted from an access position to a separate position. As a result of it, the needle thread is fully tightened by being operated together with the feeding movement while restricted, and is fed to a thread take-up lever from a thread-spooling piece, which is necessary for forming the next stitch.