Abstract: A thread checking device is installed in combination with a sewing machine in order to exert a proper tension on the thread loop formed at the eye of the needle when the thread loop passes through betweeen the bobbin case and the rotation stopping member for restraining rotation of the bobbin case. This thread checking device is provided with thread suspending means which comprises a thread suspending part disposed near a specified position where the thread guide of the thread take-up member is located when the needle thread loop passes between the bobbin case and the rotation stopping member. The thread suspending means suspends the needle thread held on the thread guide with the suspending part when the take-up member moves from the maximum thread take-up position to the maximum thread slack position.