To obtain a yacon processed food product soaked in sugar intended for solving such problems that, as it is difficult to preserve tuberous root (yam) of yacon raw as it is for a long period, there is a method for preserving by processing, but as yacon has a lot of water content, the components are washed away together with the water content when soaking in sugar, and also a processed food product soaked in sugar is difficult to produce without making sugar content high.

The yacon processed food product soaked in sugar is obtained by washing the tuberous root (yam) of yacon followed by peeling, cutting the yacon in a necessary shape followed by heat treatment, evaporating the water content by sunlight followed by subjecting to concentration treatment, infiltrating sugar content into the product through soaking in a sugar solution so as to control the sugar concentration to ≤75% and covering sugar or no sugar on the product. The processed food product soaked in the sugar is used as confectionery as it is. The subject compound confectionery is also obtained by mixing or adding the processed food product with/to other confectionery.