1. A vehicle data analysis method for analyzing vehicle data reflecting a driver's driving operation, comprising: collecting a plurality of pieces of vehicle data based on a plurality of types of driving operations; grouping these collected pieces of the vehicle data into at least two groups based on an evaluation criterion that is an index for evaluating a level of the driving operation; extracting characteristic values of vehicle data differing between the groups; and obtaining a degree of influence exerted by the extracted characteristic value of vehicle data on the vehicle data evaluated based on the evaluation criterion.