A manufacturing method of a silicone rubber foam, comprising: a step of irradiating a composition for silicone rubber foam comprising 100 parts by mass of alkenyl group-containing polyorganosiloxane expressed by a following general formula, having a mass average degree of polymerization of 4,000 to 10,000 and having two or more R 2 s in the following general formula as a content per mass in a molecule at a rate of 0.001 mmol/g or more and less than 0.3 mmol/g, where R 1 represents an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated group, R 2 represents an alkenyl group, R 3 represents a monovalent group indicating each independent R 1 or R 2, n and m represent the total numbers of each recurring unit obtained by random polymerization or block polymerization, and n+m+2 obtained by adding 2 that is the number of terminal groups to n and m represents a mass average degree of polymerization; an amount of polyorganohydrogensiloxane having an average of two or more hydrogen atoms bonded to a silicon atom in a molecule so that a molar ratio of the silicon-atom-bonded hydrogen atoms to the alkenyl groups in the component (the number of moles of hydrogen atoms bonded to the silicon atoms in the component/the number of moles of the alkenyl groups in the component) is 0.001 to 5; 0.1 to 10 parts by mass of an organic foaming agent with a decomposition temperature of 50 to 250°C; 5 to 200 parts by mass of silica powder; and a catalyst amount of a platinum-based metal compound catalyst activated with ultraviolet rays, with ultraviolet rays at a temperature lower than the decomposition temperature of the organic foaming agent to obtain a cross-linked body; and a step of heat-treating the cross-linked body at a temperature equal to or higher than the decomposition temperature of the organic foaming agent to obtain a silicone rubber foam. a step of irradiating a composition for silicone rubber foam comprising 100 parts by mass of alkenyl group-containing polyorganosiloxane expressed by a following general formula, having a mass average degree of polymerization of 4,000 to 10,000 and having two or more R 2 s in the following general formula as a content per mass in a molecule at a rate of 0.001 mmol/g or more and less than 0.3 mmol/g, where R 1 represents an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated group, R 2 represents an alkenyl group, R 3 represents a monovalent group indicating each independent R 1 or R 2, n and m represent the total numbers of each recurring unit obtained by random polymerization or block polymerization, and n+m+2 obtained by adding 2 that is the number of terminal groups to n and m represents a mass average degree of polymerization; an amount of polyorganohydrogensiloxane having an average of two or more hydrogen atoms bonded to a silicon atom in a molecule so that a molar ratio of the silicon-atom-bonded hydrogen atoms to the alkenyl groups in the component (the number of moles of hydrogen atoms bonded to the silicon atoms in the component/the number of moles of the alkenyl groups in the component) is 0.001 to 5; 0.1 to 10 parts by mass of an organic foaming agent with a decomposition temperature of 50 to 250°C; 5 to 200 parts by mass of silica powder; and a catalyst amount of a platinum-based metal compound catalyst activated with ultraviolet rays, with ultraviolet rays at a temperature lower than the decomposition temperature of the organic foaming agent to obtain a cross-linked body; and 100 parts by mass of alkenyl group-containing polyorganosiloxane expressed by a following general formula, having a mass average degree of polymerization of 4,000 to 10,000 and having two or more R 2 s in the following general formula as a content per mass in a molecule at a rate of 0.001 mmol/g or more and less than 0.3 mmol/g, where R 1 represents an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated group, R 2 represents an alkenyl group, R 3 represents a monovalent group indicating each independent R 1 or R 2, n and m represent the total numbers of each recurring unit obtained by random polymerization or block polymerization, and n+m+2 obtained by adding 2 that is the number of terminal groups to n and m represents a mass average degree of polymerization; an amount of polyorganohydrogensiloxane having an average of two or more hydrogen atoms bonded to a silicon atom in a molecule so that a molar ratio of the silicon-atom-bonded hydrogen atoms to the alkenyl groups in the component (the number of moles of hydrogen atoms bonded to the silicon atoms in the component/the number of moles of the alkenyl groups in the component) is 0.001 to 5; 0.1 to 10 parts by mass of an organic foaming agent with a decomposition temperature of 50 to 250°C; 5 to 200 parts by mass of silica powder; and a catalyst amount of a platinum-based metal compound catalyst activated with ultraviolet rays, with ultraviolet rays at a temperature lower than the decomposition temperature of the organic foaming agent to obtain a cross-linked body; and a step of heat-treating the cross-linked body at a temperature equal to or higher than the decomposition temperature of the organic foaming agent to obtain a silicone rubber foam.