A coating agent comprising: a polyorganosiloxane represented by the following general formula: wherein R 1 's and R 2 's each independently represent a monovalent hydrocarbon group, R 1' 's each independently represent a monovalent hydrocarbon group or a hydroxy group (-OH group), and m is an integer of 2,000 to 30,000; a polydiorganosiloxane represented by the following general formula: wherein R 3 's and R 4 's each independently represent a monovalent hydrocarbon group, and n is an integer of 8 to 1,000; and one of an amino group-containing polyorganosiloxane containing at least one amino group per molecule represented by the following general formula: wherein R 5 's each independently represent a monovalent hydrocarbon group or an -OR 8 group, wherein R 8 's each independently represent a substituted or unsubstituted monovalent hydrocarbon group having 1 to 4 carbon atoms, R 6 's and R 7 's each independently represent a monovalent hydrocarbon group, A's each independently represent an amino group-containing group, p:q = 5 to 100:1, and q is an integer of 1 to 100, and a hydroxy group-containing polyorganosiloxane represented by the following general formula: wherein R 9 's and R 9' 's each independently represent a monovalent hydrocarbon group or a hydroxy group (-OH), provided that at least one of R 9 's and at least one of R 9' 's are a hydroxy group (-OH), R 10 's each independently represent a monovalent hydrocarbon group, and r is an integer of 1,000 to 30,000. a polyorganosiloxane represented by the following general formula: wherein R 1 's and R 2 's each independently represent a monovalent hydrocarbon group, R 1' 's each independently represent a monovalent hydrocarbon group or a hydroxy group (-OH group), and m is an integer of 2,000 to 30,000; wherein R 1 's and R 2 's each independently represent a monovalent hydrocarbon group, R 1' 's each independently represent a monovalent hydrocarbon group or a hydroxy group (-OH group), and m is an integer of 2,000 to 30,000; a polydiorganosiloxane represented by the following general formula: wherein R 3 's and R 4 's each independently represent a monovalent hydrocarbon group, and n is an integer of 8 to 1,000; and one of wherein R 3 's and R 4 's each independently represent a monovalent hydrocarbon group, and n is an integer of 8 to 1,000; and one of an amino group-containing polyorganosiloxane containing at least one amino group per molecule represented by the following general formula: wherein R 5 's each independently represent a monovalent hydrocarbon group or an -OR 8 group, wherein R 8 's each independently represent a substituted or unsubstituted monovalent hydrocarbon group having 1 to 4 carbon atoms, R 6 's and R 7 's each independently represent a monovalent hydrocarbon group, A's each independently represent an amino group-containing group, p:q = 5 to 100:1, and q is an integer of 1 to 100, and wherein R 5 's each independently represent a monovalent hydrocarbon group or an -OR 8 group, wherein R 8 's each independently represent a substituted or unsubstituted monovalent hydrocarbon group having 1 to 4 carbon atoms, R 6 's and R 7 's each independently represent a monovalent hydrocarbon group, A's each independently represent an amino group-containing group, p:q = 5 to 100:1, and q is an integer of 1 to 100, and a hydroxy group-containing polyorganosiloxane represented by the following general formula: wherein R 9 's and R 9' 's each independently represent a monovalent hydrocarbon group or a hydroxy group (-OH), provided that at least one of R 9 's and at least one of R 9' 's are a hydroxy group (-OH), R 10 's each independently represent a monovalent hydrocarbon group, and r is an integer of 1,000 to 30,000. wherein R 9 's and R 9' 's each independently represent a monovalent hydrocarbon group or a hydroxy group (-OH), provided that at least one of R 9 's and at least one of R 9' 's are a hydroxy group (-OH), R 10 's each independently represent a monovalent hydrocarbon group, and r is an integer of 1,000 to 30,000.