A catalyst composition comprising: dialkyl L-tartrate; and one or more selected from the group consisting of a transition metal compound represented by the following Formula 1 and a transition metal compound represented by the following Formula 3: wherein M is ruthenium or osmium, A is oxygen (O), nitrogen (N), or sulfur (S), and if A is oxygen (O) or sulfur (S), any one of R 10 and R 11 does not exist, X 1 and X 2 are each independently halogen, R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms, R 7 and R 8 are each independently hydrogen or an electron withdrawing group, R 9 is a direct bond or an alkylene group having 1 to 10 carbon atoms, and R 10 and R 11 are each independently an alkyl group having 1 to 10 carbon atoms or a substituent represented by the following Formula 2, wherein Y is oxygen (O), nitrogen (N), or sulfur (S), and if Y is oxygen (O) or sulfur (S), any one of R 13 and R 14 does not exist, R 12 is an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an arylene group having 6 to 10 carbon atoms, R 13 and R 14 are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms, and * represents a bonding position with A, wherein M is ruthenium or osmium, R 1 and R 2 are each independently hydrogen or a substituent represented by the following Formula 4, and at least one of R 1 or R 2 is a substituent represented by the following Formula 4, X 1 and X 2 are each independently halogen, and Ph is a phenyl group, and wherein R 3 and R 4 are each independently an alkyl group having 1 to 10 carbon atoms; or R 3 and R 4 are linked together, and with N to which they are attached to form a saturated or unsaturated 5-membered ring. M is ruthenium or osmium, A is oxygen (O), nitrogen (N), or sulfur (S), and if A is oxygen (O) or sulfur (S), any one of R 10 and R 11 does not exist, X 1 and X 2 are each independently halogen, R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms, R 7 and R 8 are each independently hydrogen or an electron withdrawing group, R 9 is a direct bond or an alkylene group having 1 to 10 carbon atoms, and R 10 and R 11 are each independently an alkyl group having 1 to 10 carbon atoms or a substituent represented by the following Formula 2, wherein Y is oxygen (O), nitrogen (N), or sulfur (S), and if Y is oxygen (O) or sulfur (S), any one of R 13 and R 14 does not exist, R 12 is an alkylene group having 1 to 10 carbon atoms, a cycloalkylene group having 3 to 10 carbon atoms, or an arylene group having 6 to 10 carbon atoms, R 13 and R 14 are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms, and * represents a bonding position with A, wherein M is ruthenium or osmium, R 1 and R 2 are each independently hydrogen or a substituent represented by the following Formula 4, and at least one of R 1 or R 2 is a substituent represented by the following Formula 4, X 1 and X 2 are each independently halogen, and Ph is a phenyl group, and wherein R 3 and R 4 are each independently an alkyl group having 1 to 10 carbon atoms; or R 3 and R 4 are linked together, and with N to which they are attached to form a saturated or unsaturated 5-membered ring. <EOS>