To obtain a urea library compound useful as a lead compound for the development of chemicals by adding an amine reactant to each reaction zone containing liquid medium, adding and reacting an isocyanate reactant and adding a scavenger to the reaction mixture.

An amine reactant of formula I (R1 and R2 are each H or a non-inhibitory substituent; R1 and R2 are not H at the same time) is added in an amount of n-equivalent to each reaction zone containing a liquid medium, 1, 1n-equivalent of a solvent-soluble isocyanate reactant of the formula R3NCO (R3 is a non-inhibitory substituent) is added to each reaction zone and the amine reactant is made to react with the isocyanate reactant. An amine-functioning scavenger supported on a solid and expressed by formula II (the group of formula III is a solid carrier insoluble in the liquid reaction medium of each reaction zone; L is a bivalent bonding group; the amine is primary or secondary amine- substituent) is added (in an amount equal to the excess equivalent of unreacted isocyanate) to each reaction zone and reacted to obtain the urea library compound of formula IV.