There is no need to get rid of your favorite pair of leather shoes just because the sole is coming loose or is detached. You can reinforce the soles on your own with a few supplies that you can purchase at a shoe store or hardware store. In just a few steps, your leather shoes will be ready for you to wear again.
Clean the exposed bottom of the shoe as well as the inner side of the sole that has become detached. Use sandpaper to gently remove any dirt, debris or glue, or the new adhesive might not stick.
Apply a fast-drying polyurethane cement adhesive to bottom of the shoe where the sole has become detached and to the inner side of the protective rubber or leather sole. If the cement did not come with an applicator, use a very small, inexpensive paint brush that you will not mind disposing of later or an ice cream-bar stick. Keep the bottom of the shoe separated from the sole, using something that will not easily stick to the cement or interfere with the adhesive, such as toothpicks. Wait 30 minutes for the adhesive to settle; it works best after it has had time to dry and become tacky.
Firmly press the loose sole to the bottom of the shoe to remove any air bubbles and apply pressure. Wipe off any excess cement with a dry cloth. This type of adhesive is quite strong, so there is no need to apply weight to the shoe. Keep the shoe upside down so no remnants of glue stick to the drying surface. Check again for any excess glue and remove. Allow an hour for the adhesive to work.
Use polyurethane-based adhesives in a well-ventilated area to avoid inhaling toxic fumes.