PROBLEM TO BE SOLVED: To provide a catalyst for hydrocarbon contact degradation having high bottom resolution, excellent in water heat stability and selectivity (high liquid yield, low gas and low coke) and to provide a method of manufacturing a modified zeolite having a structure suitable for the catalyst.SOLUTION: A method of manufacturing a modified zeolite includes following processes (a) to (c). (a) a process of adding acid to a super stable zeolite (USY: Ultra-Stable Y) dispersion. (b) a process of adding an acidic aluminum solution. (c) a process of adding alkaline to adjust pH to 5.0 to 9.5. A catalyst for hydrocarbon contact degradation contains the modified zeolite and a matrix component and the content of the modified zeolite is in a range of 10 to 50 mass% based on the total amount of the catalyst as a solid content.
