Disclosed is a novel hybrid wiggler as a kind of insertion devices, for example, in an electron accelerator. Different from a conventional hybrid wiggler consisting of two oppositely facing arrays each formed of an alternate arrangement of a plurality of permanent magnet blocks and a plurality of pole pieces of a soft magnetic material to generate a sine-curved periodical magnetic field in the gap space between the arrays to cause meandering of electron beams, each of the pole pieces is sandwiched on the lateral surfaces with a pair of auxiliary permanent magnet blocks so that the periodical magnetic field generated in the gap space can be greatly strengthened.