The mutual control of electricity and magnetism in a solid has been an important topic for long, and is currently of increasing interest in the light of application to new electronic devices. One important issue is the realization of gigantic magnetoelectric effect, i.e. the function that the magnetization (electric polarization) can be effectively produced by electric (magnetic) field. Recently, the authors’ group has developed the new multiferroic, the material in which ferroelectricity and magnetism can coexist, as the promising host of the large magnetoelectric effect. We are developing versatile and flexible magnetic controls of the electronic polarization vector with use of multiferroics. Toward the electric control of magnetism in a solid, we will explore new or tailor-made multiferroics as well as new control principles.