This application relates to an input data generating apparatus for generating forcing data used as input data for a climate change prediction model. In one aspect, the apparatus includes a memory storing instructions and a processor configured to, by executing the instructions, collect new ground type data from land-use harmonization (LUH) data that is restored through history database of the global environment (HYDE) and provided by the coupled model inter-comparison project (CMIP). The processor may also collect existing ground type data calculated by an existing model in a previous phase of the CMIP, generate aggregated ground type data by data-aggregating the new ground type data and the existing ground type data, with priority to the new ground type data. The processor may further generate the forcing data from the aggregated ground type data by performing a distortion correction on a data distortion that occurs during the data aggregation.