A method of caching mapping table for use in a flash memory device having a flash memory controller and a flash memory is provided. The method includes: in response to a host read/write command, checking a G2F mapping table to determine whether a required group of a L2P mapping table has been loaded to a DRAM of the flash memory controller and accordingly obtain a node index indicating which memory node of the DRAM the group is stored in; recording the node index to a first region of a SRAM of the flash memory controller; accessing the DRAM to obtain an L2P address indicating a physical address that is associated with the host read/write command from the group of the L2P mapping table by referencing the node index stored in the first region of the SRAM; and performing a read/write operation on the flash memory according to the L2P address.