PURPOSE:To obtain a foamable ligneous resin particle giving a foam which has excellent biodegradability and is easily incinerated by incorporating a foaming agent into a chemically modified wood which is not in a solution state. CONSTITUTION:This resin particle is one obtained by incorporating a foaming agent into a chemically modified wood which is not in a solution state. Preferred examples of the chemical modification are etherification represented by benzylation and esterification represented by acetylation. Preferred examples of the chemically modified wood include a wood or cellulosic material modified by etherification, in particular by benzylation or the incorporation of a group analogous to benzyl, and a wood or cellulosic material modified by esterification, in particular by acetylation or the incorporation of a group analogous to acetyl.