A novel modified wiggler for higher harmonic lasing, modified wiggler, has been developed at ILT/ILE. Its magnetic field is expressed as the sum of the harmonic magnetic field components. A trial modified wiggler produced a considerable harmonic field component. A modification ratio, B-3/B-1, of more than 10% was achieved. Using this wiggler, we observed the enhanced 3rd harmonic spontaneous emission. Further, the development of a modified wiggler for harmonic lasing will be presented.