To provide an excellent antistatic agent and a multilayer polyolefin synthetic resin film and sheet excellent in an antistatic effect and its durability.

The antistatic agent comprises a graft compound prepared by reacting a diol-type polyoxyalkylene compound (A) and a monool-type polyoxyalkylene compound (B) with an acid-modified polyolefin having a specific saponification value and a molecular weight in a specific ratio. The antistatic agent is added to the multilayer polyolefin synthetic resin film and sheet in an amount of 3-20 wt.% of the weight of the surface layers, wherein the sum of the thickness of both surface layers is 5-50% relative to the total thickness of the film and sheet.