Cordless window covering

A cordless window covering, comprising:

• a first rail;
• a covering body, having a first edge disposed on one side of the first rail and a second edge opposing to the first edge;
• a second rail, connected to the second edge of the covering body so that the covering body is located between the first rail and the second rail;
• a first pulling cord and a second pulling cord;
• and
• a cord-retracting device, disposed in the first rail and comprising:
• a first casing;
• a power assembly, situated on the first casing;
• a first reeling wheel, rotatably disposed on the first casing;
• a second reeling wheel, rotatably disposed on the first casing and connected to the first reeling wheel in which the first reeling wheel and the second reeling wheel can be driven by each other to rotate concurrently;
• and
• an adjusting member, situated on the first casing and movable with respect to the first casing;
• wherein a first end of the first pulling cord and a first end of the second pulling cord are respectively connected to the first reeling wheel and the second reeling wheel, and a second end of the first pulling cord and a second end of the second pulling cord extend in opposite directions after respectively going around the adjusting member, such that the first pulling cord and the second pulling cord respectively apply a first force and a second force in opposite directions to the adjusting member;
• wherein when the first force does not substantially equal to the second force, the adjusting member moves with respect to the first casing towards a side with greater force, and one of the first pulling cord and the second pulling cord applying greater force to the adjusting member than the other has a length thereof located between the first rail and the second rail elongate along with movement of the adjusting member.