To provide a compounding agent for a moisture curing compsn, which can give a moisture curing compsn. having enough curing rate even at a low temperature and excellent characteristics, that is, good storage stability and little volume reduction after curing.

This compounding agent for a moisture curing compsn. satisfies the following conditions (a)-(d), and this moisture curing compsn. is manufactured by using it. (a) It contains ethylenoxy group and its content is not lower than 20 wt.%. (b) It does not contain an active hydrogen. (c) It has a b.p. higher than 130°C or no b.p. (d) Its mol.wt. is not lower than 100 and not higher than 800.