A hydrosilylation reaction catalyst consisting of: (i) a metal salt compound having the formula: M a b c wherein M is a transition metal selected from Fe, Co, Ru, Ni, and Rh, X is a halogen atom, L is a monovalent organic group of at least one type selected from the formulae to, a is an integer of 1 or 2, b is an integer of 0 to 6, c is an integer of 0 to 3, satisfying b+c = 2 or 3 when a is 1, and b+c = 4 to 6 when a is 2, provided that when M is Fe, a is 1, b is 2 and c is 0, -O-R 1 -OCO-R 1 -OSO 2 -R 1 wherein each R 1 independently is C 1 -C 30 monovalent hydrocarbon group, which may be substituted with halogen atoms, methoxy, ethoxy, propoxy, or dialkylamino groups, or a monovalent organic group having the formula: - p -R 2 wherein A is a C 1 -C 30 divalent hydrocarbon group which may be substituted with halogen, p is an integer of 0 or 1, satisfying p = 0 or 1 when L is a monovalent organic group having formula, and p = 1 when L is a monovalent organic group having formula or, R 2 is a group having the formula: -{Si(R 3) 2 -R 4} s -Si(R 3) d {[(OSi(R 3) 2)] f -R 3} e wherein each R 3 independently is C 1 -C 20 alkyl group, C 1 -C 20 alkoxy group, C 6 -C 20 aryl group or C 7 -C 20 aralkyl group, which may be substituted with halogen atoms, methoxy, ethoxy, propoxy, or dialkylamino groups, R 4 is a C 1 -C 10 divalent hydrocarbon group, s is an integer of 0 or 1, d is an integer of 0 to 3, e is an integer of 0 to 3, satisfying d+e = 3, and f is an integer of 1, and (ii) a carbene compound having one or two adjoining nitrogen atoms, represented by the formula: wherein Z is a C 2 -C 5 divalent organic group which may contain a nitrogen atom and/or unsaturated bond, R 4 and R 5 are each independently a C 1 -C 30 alkyl, aryl or aralkyl group which may be substituted with a halogen atom or alkoxy group. (i) a metal salt compound having the formula: M a b c wherein M is a transition metal selected from Fe, Co, Ru, Ni, and Rh, X is a halogen atom, L is a monovalent organic group of at least one type selected from the formulae to, a is an integer of 1 or 2, b is an integer of 0 to 6, c is an integer of 0 to 3, satisfying b+c = 2 or 3 when a is 1, and b+c = 4 to 6 when a is 2, provided that when M is Fe, a is 1, b is 2 and c is 0, -O-R 1 -OCO-R 1 -OSO 2 -R 1 wherein each R 1 independently is C 1 -C 30 monovalent hydrocarbon group, which may be substituted with halogen atoms, methoxy, ethoxy, propoxy, or dialkylamino groups, or a monovalent organic group having the formula: - p -R 2 wherein A is a C 1 -C 30 divalent hydrocarbon group which may be substituted with halogen, p is an integer of 0 or 1, satisfying p = 0 or 1 when L is a monovalent organic group having formula, and p = 1 when L is a monovalent organic group having formula or, R 2 is a group having the formula: -{Si(R 3) 2 -R 4} s -Si(R 3) d {[(OSi(R 3) 2)] f -R 3} e wherein each R 3 independently is C 1 -C 20 alkyl group, C 1 -C 20 alkoxy group, C 6 -C 20 aryl group or C 7 -C 20 aralkyl group, which may be substituted with halogen atoms, methoxy, ethoxy, propoxy, or dialkylamino groups, R 4 is a C 1 -C 10 divalent hydrocarbon group, s is an integer of 0 or 1, d is an integer of 0 to 3, e is an integer of 0 to 3, satisfying d+e = 3, and f is an integer of 1, and wherein M is a transition metal selected from Fe, Co, Ru, Ni, and Rh, X is a halogen atom, L is a monovalent organic group of at least one type selected from the formulae to, a is an integer of 1 or 2, b is an integer of 0 to 6, c is an integer of 0 to 3, satisfying b+c = 2 or 3 when a is 1, and b+c = 4 to 6 when a is 2, provided that when M is Fe, a is 1, b is 2 and c is 0, -O-R 1 -OCO-R 1 -OSO 2 -R 1 X is a halogen atom, L is a monovalent organic group of at least one type selected from the formulae to, a is an integer of 1 or 2, b is an integer of 0 to 6, c is an integer of 0 to 3, satisfying b+c = 2 or 3 when a is 1, and b+c = 4 to 6 when a is 2, provided that when M is Fe, a is 1, b is 2 and c is 0, -O-R 1 -OCO-R 1 -OSO 2 -R 1 wherein each R 1 independently is C 1 -C 30 monovalent hydrocarbon group, which may be substituted with halogen atoms, methoxy, ethoxy, propoxy, or dialkylamino groups, or a monovalent organic group having the formula: - p -R 2 wherein A is a C 1 -C 30 divalent hydrocarbon group which may be substituted with halogen, p is an integer of 0 or 1, satisfying p = 0 or 1 when L is a monovalent organic group having formula, and p = 1 when L is a monovalent organic group having formula or, R 2 is a group having the formula: -{Si(R 3) 2 -R 4} s -Si(R 3) d {[(OSi(R 3) 2)] f -R 3} e p is an integer of 0 or 1, satisfying p = 0 or 1 when L is a monovalent organic group having formula, and p = 1 when L is a monovalent organic group having formula or, R 2 is a group having the formula: -{Si(R 3) 2 -R 4} s -Si(R 3) d {[(OSi(R 3) 2)] f -R 3} e wherein each R 3 independently is C 1 -C 20 alkyl group, C 1 -C 20 alkoxy group, C 6 -C 20 aryl group or C 7 -C 20 aralkyl group, which may be substituted with halogen atoms, methoxy, ethoxy, propoxy, or dialkylamino groups, R 4 is a C 1 -C 10 divalent hydrocarbon group, s is an integer of 0 or 1, d is an integer of 0 to 3, e is an integer of 0 to 3, satisfying d+e = 3, and f is an integer of 1, and (ii) a carbene compound having one or two adjoining nitrogen atoms, represented by the formula: wherein Z is a C 2 -C 5 divalent organic group which may contain a nitrogen atom and/or unsaturated bond, R 4 and R 5 are each independently a C 1 -C 30 alkyl, aryl or aralkyl group which may be substituted with a halogen atom or alkoxy group.