A curable composition comprising: a condensation product having a weight average molecular weight of 30,000 or less; and a curing agent which cures an epoxy group, the condensation product being obtainable by hydrolysis and condensation of a silane compound and a silane compound in the presence of a neutral salt catalyst, a molar ratio of the silane compound to the silane compound being 0 or more and 9 or less, the condensation product having a ratio Y/X of 0.2 or less, where X is the number of moles of an OR 3 group directly bonded to silicon atoms of the silane compounds and which are materials of the condensation product and Y is the number of moles of an OR 3 group directly bonded to a silicon atom of the condensation product, the silane compound having a hydrolyzable silyl group and being represented by the following General Formula: R 1 -(SiR 2 a (OR 3) 3-a), wherein R 1 is an alkyl group having 1 to 10 carbon atoms and having a terminal substituted with an epoxy structure-containing group, each R 2 is independently a hydrogen atom or a monovalent hydrocarbon group selected from among an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, each R 3 is independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and a is an integer of 0 to 2, and the silane compound having a hydrolyzable silyl group and being represented by the following General Formula: R 4 -(SiR 2 a (OR 3) 3-a), wherein R 4 is a group having no epoxy structure-containing group and selected from among a substituted or unsubstituted alkyl group, an alkenyl group, and a substituted aryl group, each of which has 1 to 10 carbon atoms, each R 2 is independently a hydrogen atom or a monovalent hydrocarbon group selected from among an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, each R 3 is independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and a is an integer of 0 to 2, wherein the neutral salt catalyst is a salt made of a combination of a cation and an anion; the cation is any one selected from the group consisting of Group 1 element ions and Group 2 element ions; and the anion is any one selected from the group consisting of a chloride ion, a bromide ion, and an iodide ion. a condensation product having a weight average molecular weight of 30,000 or less; and a curing agent which cures an epoxy group, the condensation product being obtainable by hydrolysis and condensation of a silane compound and a silane compound in the presence of a neutral salt catalyst, a molar ratio of the silane compound to the silane compound being 0 or more and 9 or less, the condensation product having a ratio Y/X of 0.2 or less, where X is the number of moles of an OR 3 group directly bonded to silicon atoms of the silane compounds and which are materials of the condensation product and Y is the number of moles of an OR 3 group directly bonded to a silicon atom of the condensation product, the silane compound having a hydrolyzable silyl group and being represented by the following General Formula: wherein R 1 is an alkyl group having 1 to 10 carbon atoms and having a terminal substituted with an epoxy structure-containing group, each R 2 is independently a hydrogen atom or a monovalent hydrocarbon group selected from among an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, each R 3 is independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and a is an integer of 0 to 2, and the silane compound having a hydrolyzable silyl group and being represented by the following General Formula: wherein R 4 is a group having no epoxy structure-containing group and selected from among a substituted or unsubstituted alkyl group, an alkenyl group, and a substituted aryl group, each of which has 1 to 10 carbon atoms, each R 2 is independently a hydrogen atom or a monovalent hydrocarbon group selected from among an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, each R 3 is independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and a is an integer of 0 to 2, wherein the neutral salt catalyst is a salt made of a combination of a cation and an anion; the cation is any one selected from the group consisting of Group 1 element ions and Group 2 element ions; and the anion is any one selected from the group consisting of a chloride ion, a bromide ion, and an iodide ion.