A dog harness is a piece of equipment for dogs, worn around a dog's torso and/or neck.  The dog harness usually has a loop structure, which surrounds a dog's torso and/or neck, and a leash attachment means to be connected to a leash.  The dog harness and leash are usually used together to restrain or control a dog, commonly used when walking a dog.  Instead of the loop structure, a garment may be used to surround a dog's torso, including a dog's chest and/or belly. 
Compared to a collar worn around a neck, a dog harness is better in preventing choking or lowering chance of slipping out of it because of its structure surrounding a dog's torso and neck and thereby distributing force.  Thus, a dog harness is growing in popularity among many dog owners, especially for those having smaller breed dogs.  The dog harness is also useful for controlling, directing and teaching the dog. 
However, a dog harness is not free from the issue of slipping out.  If a dog trying to move forward or backward against the direction of the leash held by a user, a dog harness may become loose and a dog may slip out of it and escape.  Especially, when a dog tries hard to move backward against the pulling force of the leash held by a user and lower its head, there may be a room formed and getting bigger between the dog's back of neck and the leash connector connecting the leash and the dog harness, thereby allowing the dog to slip out and escape the dog harness. 
Therefore, to solve the above problems, there is a need for a dog harness having a freely moving leash strap for tightening and fastening the dog's torso when the dog tries to move backwards to escape from the dog harness.  This invention is directed to solve these problems and satisfy the long-felt need.