A curable composition comprising: an organic compound having at least 2 carbon-carbon double bonds per molecule, the carbon-carbon double bond being reactive with a SiH group; a modified polyorganosiloxane compound; and a hydrosilyation catalyst, wherein: the modified polyorganosiloxane compound having at least two SiH groups per molecule, and being a hydrosilylation reaction product of the following compounds (α) and (β): (α) an organic compound having two to six carbon-carbon double bonds per molecule, the carbon-carbon double bonds being reactive with an SiH group, (β) a cyclic polyorganosiloxane including the following general formula: wherein R 1 to R 3 are identical or different monovalent substituted or unsubstituted hydrocarbon groups; p is an integer of 1 to 8, q is an integer of 2 to 6, the p and q being integers that satisfy; 3 ≤ p + q ≤ 10, the cyclic polyorganosiloxane produced by a method comprising: decomposing a polyorganosiloxane by heating the polyorganosiloxane in the presence of a catalyst the polyorganosiloxane having a mani chain skeleton represented by the following general formula: wherein R 1 to R 3 are identical or different monovalente substituted or unsubstituted hydrocarbon groups; and m and n satisfy: 0.3 ≤ n / (m + n) < 0.9 and further comprising the following compounds (β1) and (β2): an organic compound having at least 2 carbon-carbon double bonds per molecule, the carbon-carbon double bond being reactive with a SiH group; a modified polyorganosiloxane compound; and a hydrosilyation catalyst, wherein: the modified polyorganosiloxane compound having at least two SiH groups per molecule, and being a hydrosilylation reaction product of the following compounds (α) and (β): (α) an organic compound having two to six carbon-carbon double bonds per molecule, the carbon-carbon double bonds being reactive with an SiH group, (β) a cyclic polyorganosiloxane including the following general formula: wherein R 1 to R 3 are identical or different monovalent substituted or unsubstituted hydrocarbon groups; p is an integer of 1 to 8, q is an integer of 2 to 6, the p and q being integers that satisfy; 3 ≤ p + q ≤ 10, the cyclic polyorganosiloxane produced by a method comprising: decomposing a polyorganosiloxane by heating the polyorganosiloxane in the presence of a catalyst the polyorganosiloxane having a mani chain skeleton represented by the following general formula: wherein R 1 to R 3 are identical or different monovalente substituted or unsubstituted hydrocarbon groups; and m and n satisfy: 0.3 ≤ n / (m + n) < 0.9 and further comprising the following compounds (β1) and (β2): the modified polyorganosiloxane compound having at least two SiH groups per molecule, and being a hydrosilylation reaction product of the following compounds (α) and (β): (α) an organic compound having two to six carbon-carbon double bonds per molecule, the carbon-carbon double bonds being reactive with an SiH group, (β) a cyclic polyorganosiloxane including the following general formula: wherein R 1 to R 3 are identical or different monovalent substituted or unsubstituted hydrocarbon groups; p is an integer of 1 to 8, q is an integer of 2 to 6, the p and q being integers that satisfy; 3 ≤ p + q ≤ 10, the cyclic polyorganosiloxane produced by a method comprising: decomposing a polyorganosiloxane by heating the polyorganosiloxane in the presence of a catalyst the polyorganosiloxane having a mani chain skeleton represented by the following general formula: wherein R 1 to R 3 are identical or different monovalente substituted or unsubstituted hydrocarbon groups; and m and n satisfy: 0.3 ≤ n / (m + n) < 0.9 and further comprising the following compounds (β1) and (β2): (α) an organic compound having two to six carbon-carbon double bonds per molecule, the carbon-carbon double bonds being reactive with an SiH group, (β) a cyclic polyorganosiloxane including the following general formula: wherein R 1 to R 3 are identical or different monovalent substituted or unsubstituted hydrocarbon groups; p is an integer of 1 to 8, q is an integer of 2 to 6, the p and q being integers that satisfy; 3 ≤ p + q ≤ 10, 3 ≤ p + q ≤ 10, the cyclic polyorganosiloxane produced by a method comprising: decomposing a polyorganosiloxane by heating the polyorganosiloxane in the presence of a catalyst the polyorganosiloxane having a mani chain skeleton represented by the following general formula: wherein R 1 to R 3 are identical or different monovalente substituted or unsubstituted hydrocarbon groups; and m and n satisfy: 0.3 ≤ n / (m + n) < 0.9 and 0.3 ≤ n / (m + n) < 0.9 and further comprising the following compounds (β1) and (β2):