To obtain a new crosslinking compound (crosslinkable functional group-having compound) which can solve the problems such as a high hygroscopicity, inferior electric characteristics, and decomposition during a reaction due to a high reaction temperature.

A 5-halogenomethylacenaphthylene is obtained by subjecting a 5-halogenomethylacenaphthene to a dehydrogenation reaction. An organic compound having n × hydroxyl groups is treated with a metalizing reagent in an organic solvent and then reacted with the 5-halogenomethylacenaphthylene to obtain the crosslinking compound of formula III [(n) is a positive integer; R is an n-valent organic group]. Preferable compounds among the crosslinking compound of formula III have thermally curing temperatures of ≤250°C, and give cured products, when heated.