To provide a life jacket capable of stably keeping a person wearing the life jacket in a state of floating on the water surface.

This life jacket A has a rear collar part 21 suspended from a collar part 1a of the life jacket main body 1 standably along a back face of a back body 11 of the life jacket main body 1, and a floating material 21a is included in the back collar part 21. Accordingly, when the person wearing this life jacket falls into the water, the rear collar part B automatically floats on the water surface, whereby the person wearing the life jacket is prevented from largely dancing by the rear collar part B to secure the breathing of the person wearing the life jacket B.