  In this paper, we consider the groupoidification of the fermion algebra. We
construct a groupoid as the categorical analogues of the fermionic Fock space,
and the creation and annihilation operators correspond to spans of groupoids.
The categorical fermionic Fock states have some extra structures comparing with
the normal forms. We also construct a 2-category of spans of groupoids
corresponding to the fermion algebra. The relations of the morphisms in this
2-category are consistent with those in the graphical category which is
represented by string diagrams.
