We study the gauge structure of vacuum string field theory expanded around
the D-brane solution, namely, the gauge transformation and the transversality
condition of the massless vector fluctuation mode. We find that the gauge
transformation on massless vector field is induced as an anomaly; an infinity
multiplied by an infinitesimal factor. The infinity comes from the singularity
at the edge of the eigenvalue distribution of the Neumann matrix, while the
infinitesimal factor from the violation of the equation of motion of the
fluctuation modes due to the regularization for the infinity. However, the
transversality condition cannot be obtained even if we take into account the
anomaly contribution.Comment: 19 pages, LaTeX2