A key management device for data encryption/decryption is provided. The key management device includes a static random-access memory (SRAM), a register, and a control circuit. The control circuit can set a key lookup table in the SRAM or the register, and manage a key database. The key database includes the SRAM and an one-time programmable (OTP) memory disposed outside the key management device, and the key database stores at least one key. The key lookup table includes a key number and metadata of each of the at least one key stored in the key database. According to a specific key number contained in a key read command or a key delete command from the processor, the control circuit reads or deletes a specific key corresponding to the specific key number in the key database.