A gel-forming silicone composition comprising, compounded in a gel-forming base composition, a silane compound having the following general formula (1) or (2): ##STR1## wherein R.sup.1 is an alkyl or aryl group, R.sup.2 is an alkyl or alkoxyalkyl group, R.sup.3 and R.sup.4 are each a hydrogen atom, a methyl group or an ethyl group, R.sup.5 is an alkyl group or an ester linkage-containing group, and a, b and n are each an integer from 0 to 2. The composition is capable of forming, under mild conditions, a silicone gel which exhibits good adherence to a variety of substrates.