  Let $(G,\sigma)$ be any signed planar graph. We show that the Alon-Tarsi
number of $(G,\sigma)$ is at most 5, generalizing a recent result of Zhu for
unsigned case. In addition, if $(G,\sigma)$ is $2$-colorable then $(G,\sigma)$
has the Alon-Tarsi number at most 4. We also construct a signed planar graph
which is $2$-colorable but not $3$-choosable.

Combinatorics