A conversion device includes processing circuitry configured to receive a programmable signature as a target to be analyzed and symbolized data and/or a log as an input value, analyze the programmable signature by using a symbolic execution engine, and output a conditional branching process executed on the input value as a constraint on the input value and receive the output constraint on the input value, perform field conversion from the constraint on the input value to an output format based on a table of field name correspondence between formats, and output a static signature.