  We investigate the spin evolution of the binary X-ray pulsar 2S 0114+650,
which possesses the slowest known spin period of $\sim 2.7$ hours. We argue
that, to interpret such long spin period, the magnetic field strength of this
pulsar must be initially $\gsim 10^{14}$ G, that is, it was born as a magnetar.
Since the pulsar currently has a normal magnetic field $\sim 10^{12}$ G, our
results present support for magnetic field decay predicted by the magnetar
model.
