A signature verification apparatus includes a determining unit configured to determine a type of a signature affixed to a document file, a first generating unit configured to, when the determining unit determines that the signature is of a first type, check the validity of a certificate contained in the signature, detect whether the document file has been tampered with based on the signature, and generate a first verification result indicating whether the signature is valid based on the check and the detection, and a second generating unit configured to, when the determining unit determines that the signature is of a second type, without checking the validity of a certificate contained in the signature, detect whether the document file has been tampered with based on the signature, and generate a second verification result indicating whether the signature is valid based on the detection.