  We identify the analogues of KMS state in topos theory. Topos KMS states can
be viewed as classes of truth objects associated with a measure \mu^\rho (in
one-to-one correspondence with an original KMS state \rho) which satisfies
topos condition analogues to the ordinary KMS conditions. Topos KMS states can
be defined both externally or internally according to whether the automorphism
group of geometric morphisms acts externally on the topos structure, or the
automorphism group is an object in the topos itself, in which case, it acts
internally. We illustrate the formalism by a simple example on the Hilbert
space $\Cl^3$.
