To provide an attaching tool of a strap for a hat, capable of attaching with a strap and also attaching to a hat not having a chin strap for wearing without a fear of being blown off even in a day of a strong wind.

This attaching tool of a strap for a hat consists of a hat attaching part 1 for attaching to a hat as freely demountable, which is divided into two parts of an upper part of the hat attaching part 2 and a lower part of the hat attaching part 3. A pin 6 is installed in the lower part of the hat attaching part 3 for piercing from the inside to the outside of the hat and a hole for holding the pin 6 is formed in the upper part of the hat attaching part 2. In the lower portion of the hat attaching part 1, a strap attaching part 4 for attaching a strap thereto, is formed.