PURPOSE: To produce a powdery polyisocyanate compound having free isocyanate groups by a simple process without much loss during production by reacting a specified silicon dioxide compound with a specified amount of a polyisocyanate in a solid phase.

CONSTITUTION: 15-70 pts.wt. silicon dioxide compound containing at least 50wt.% silicon dioxide component and having an oil absorption of 100ml/100g or above is reacted with 85-30 pts.wt. polyisocyanate to obtain a powdery polyisocyanate compound having free isocyanate groups. The obtained compound has excellent long-term stability of its isocyanate groups, a small particle diameter, good powder flowing properties and little blocking property. The production process comprises feeding a dehydrated and dried silicon dioxide compound into a mixing/reactor, feeding a heated polyisocyanate in a liquid state and mixing and reacting the mixture at 30-120°C for 10min to 8hr. The progress of the reaction can be followed by measuring the concentration of the NCO groups, and the NCO concentration decreases to one corresponding to about 5-40% of the NCO concentration of the unreacted mixture when the reaction is complete.