This study was conducted to the recycling possibilities of the melted slag that was produced by gasfication and melting municipal solid waste as fine aggregate of the concrete. It was shown that the physical properties of melted slag were almost equivalent to the relevant KS standards, with the exception of solids content. When the substitution of melted slag in the mortar was increased, the flow and compressive strength of mortar decreased, while the separation of the component materials was not occurred. In case of 100 % slag substitution, compressive strength was 30～40 MPa, which showed the potential of concrete use. The length change of the mortar was acceptable. In the test of neutralization depth, the depth became deeper according to increase of exposure time and melted slag substitution ratio. Freezing resistance of slag substituted mortar was higher than plain one because compression strength became higher according to increase of slag substitution. But this tendency was disappeared with repeated thawing-freezing cycles. Specifically, the interlocking block with 25 % substitution of melted slag could meet the KS standards. It was concluded that the melted slag that was produced from incineration ash of domestic waste could be substituted to some extent as the fine aggregate in concrete.