Needle-threading device for sewing machine and sewing machine equipped with said device

A needle-threading device for a sewing machine, the needle-threading device comprising:

• a needle-threading shaft that is parallel to a vertically-moving needle bar and that is vertically movable and rotatable;
• a control lever that lowers and rotates the needle-threading shaft;
• a needle-threading end section provided at a lower end of the needle-threading shaft and having a needle-threading hook;
• and
• a needle-threading stopper provided at the needle bar and defining a lowered stoppage position of the needle-threading shaft,
• wherein the needle-threading end section lowered by operating the control lever rotates at the lowered stoppage position and causes the needle-threading hook to be inserted through a needle hole of one needle of a plurality of needles provided at the needle bar,
• wherein the needle-threading end section includes a sliding body that vertically moves relative to the needle-threading shaft, a positioning body slidable relative to the sliding body, and an interlocking mechanism that vertically moves the sliding body relative to the needle-threading shaft in accordance with sliding of the positioning body, and
• wherein the interlocking mechanism includes a reference pin provided at the needle-threading shaft and a slot cam that is provided in the positioning body and with which the reference pin is in slidably contact, the slot cam having at least three stepped cam surfaces corresponding to at least three different heights of needle holes respectively in the plurality of needles.