A thermally conductive polysiloxane composition comprising: a thermally conductive filler; a siloxane compound represented by the following general formula: wherein: R 1 is a group having an alkoxysilyl group with 1 to 4 carbon atoms; R 2 is a group having a siloxane unit represented by the following general formula: wherein each R 4 is independently a monovalent hydrocarbon group having 1 to 12 carbon atoms, Y is a group selected from the group consisting of R 1, R 4, and an aliphatic unsaturated group, and d is an integer of 2 to 500 or a monovalent hydrocarbon group having 6 to 18 carbon atoms; each X is independently a divalent hydrocarbon group having 2 to 10 carbon atoms; each of a and b is independently an integer of 1 or more; c is an integer of 0 or more; a + b + c is an integer of 4 or more; and each R 3 is independently a monovalent hydrocarbon group having 1 to 6 carbon atoms, or a hydrogen atom; an alkoxysilane compound represented by the following general formula: R 11 e R 12 f Si(OR 13) 4-(e+f) wherein each R 11 is independently an alkyl group having 6 to 18 carbon atoms, each R 12 is independently an unsubstituted or substituted acyclic monovalent hydrocarbon group having 1 to 5 carbon atoms, an unsubstituted or substituted cycloalkyl group, an unsubstituted or substituted aryl group, or an unsubstituted or substituted aralkyl group, each R 13 is independently an alkyl group having 1 to 6 carbon atoms, e is an integer of 1 to 3, and f is an integer of 0 to 2, with the proviso that e + f is an integer of 1 to 3; a polyorganosiloxane containing at least one aliphatic unsaturated group per molecule; a polyorganohydrogensiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule; and a platinum-based catalyst. a thermally conductive filler; a siloxane compound represented by the following general formula: wherein: R 1 is a group having an alkoxysilyl group with 1 to 4 carbon atoms; R 2 is a group having a siloxane unit represented by the following general formula: wherein each R 4 is independently a monovalent hydrocarbon group having 1 to 12 carbon atoms, Y is a group selected from the group consisting of R 1, R 4, and an aliphatic unsaturated group, and d is an integer of 2 to 500 or a monovalent hydrocarbon group having 6 to 18 carbon atoms; each X is independently a divalent hydrocarbon group having 2 to 10 carbon atoms; each of a and b is independently an integer of 1 or more; c is an integer of 0 or more; a + b + c is an integer of 4 or more; and each R 3 is independently a monovalent hydrocarbon group having 1 to 6 carbon atoms, or a hydrogen atom; R 1 is a group having an alkoxysilyl group with 1 to 4 carbon atoms; R 2 is a group having a siloxane unit represented by the following general formula: or a monovalent hydrocarbon group having 6 to 18 carbon atoms; each X is independently a divalent hydrocarbon group having 2 to 10 carbon atoms; each of a and b is independently an integer of 1 or more; c is an integer of 0 or more; a + b + c is an integer of 4 or more; and each R 3 is independently a monovalent hydrocarbon group having 1 to 6 carbon atoms, or a hydrogen atom; an alkoxysilane compound represented by the following general formula: R 11 e R 12 f Si(OR 13) 4-(e+f) wherein each R 11 is independently an alkyl group having 6 to 18 carbon atoms, each R 12 is independently an unsubstituted or substituted acyclic monovalent hydrocarbon group having 1 to 5 carbon atoms, an unsubstituted or substituted cycloalkyl group, an unsubstituted or substituted aryl group, or an unsubstituted or substituted aralkyl group, each R 13 is independently an alkyl group having 1 to 6 carbon atoms, e is an integer of 1 to 3, and f is an integer of 0 to 2, with the proviso that e + f is an integer of 1 to 3; a polyorganosiloxane containing at least one aliphatic unsaturated group per molecule; a polyorganohydrogensiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule; and a platinum-based catalyst.