To use more effectively an incineration ash by a method wherein a waste storage container is constituted by using a cement including an incineration ash as raw materials, and the waste storage container is placed in a waste disposal field without a fear of leak of harmful components of the waste strage.

This waste storage container comprises a container main body 1 having a space 1a for waste strage, and a leg part 2 provided on a bottom surface of the container main body 1. The container main body 1 has a rectangular parallelepiped external form, and is composed of a mortar or concrete using cement including one or more kinds of a municipal waste incineration ash, and a sewage sludge incineration ash as raw materials. The leg part 2 is also composed of the mortar or the concrete using the above cement, and the mortar or the concrete becoming the leg part 2 is placed in a form. After curing, the mortar or the concrete becoming the container main body 1 is successively placed.