To provide a swimming auxiliary tool for underwater therapeutic exercise while wearing a float jacket main body on the back by causing a left shoulder fixing sleeve part to which a left sleeve fixing part hook-and-loop fastener is fixed and a right shoulder fixing sleeve part to which a right sleeve fixing part hook-and-loop fastener to be fixed to the sleeve fixing part stopping part hook-and-loop fastener of the float jacket body in the upper half of the back of the float jacket main body made of a single bubble sponge rubber etc. having a material excellent in water floatation.

At the surface of the upper middle part of the float jacket body made of the single bubble sponge rubber etc. having the material excellent in water floatation, a rear neck support part is provided. On the surface of the float jacket body, a front recess part is provided. On the upper surface of the float jacket, a neck front recess part is provided. On the left and right surfaces of the upper part of the float jacket body, the left shoulder fixing sleeve part to which the left sleeve fixing part hook-and-loop fastener is fixed and the right shoulder fixing sleeve part to which the right sleeve fixing part hook-and-loop fastener is fixed are provided. The sleeve fixing part stopping part hook-and-loop fastener is fixed to the lower surface of the float jacket body.