A detection device includes a processing device and a storage medium. The processing device stores a result of reading a reference servo pattern by a servo reading element in the storage medium as an ideal waveform signal, acquires a servo band signal which is a result of reading a servo pattern recorded in a servo band by the servo reading element, and detects a servo pattern signal which is a result of reading the servo pattern by the servo reading element by comparing the ideal waveform signal with the servo band signal. The reference servo pattern is recorded between a BOT section and an EOT section in a longitudinal direction of the magnetic tape.