The S-type, 200-km-sized asteroid (6) Hebe has been recently indicated as a potential parent body of the ordinary chondrite meteorites. We report polarimetric observations of Hebe, which show a 0.17% variation of the degree of linear polarization p over a rotational cycle, and a small variation of the position angle θ of the polarization plane with a frequency of twice the rotation rate. These results indicate that Hebe's surface is optically heterogeneous, probably as a consequence of albedo and/or texture changes. Rotationally resolved spectroscopic observations are needed to assess whether the surface is also compositionally heterogeneous. This would rule it out as a possible source of undifferentiated meteorites, such as the ordinary chondrites.