Bissilylamino group-bearing chlorosilane compounds of formula (1): [(CH.sub.3).sub.3Si].sub.2NCH.sub.2CH.sub.2CH.sub.2Si(CH.sub.3).sub.nCl.s- ub.3-n (1) wherein n is 0 or 1 are novel. They are useful as silane coupling agents and surface treating agents. They can be readily converted, through reaction with alcohols, to bissilyl group-bearing alkoxysilane compounds which are useful as intermediates for the synthesis of aminopropyl-modified silicone oil. The invention also provides an industrially advantageous method capable of preparing the bissilylamino group-bearing chlorosilane compounds.