  By first-principles calculations, we present a doping-dependent phase diagram
of LaO{\it M}As ({\it M}=V--Cu) family. It is characterized as
antiferromagnetic semiconductor around LaOMnAs side and ferromagnetic metal
around LaOCoAs. Both LaOFeAs and LaONiAs, where superconductivity were
discovered, are located at the borderline of magnetic phases. Extensive Fermi
surface analysis suggests that the observed superconductivity is of
electron-type in its origin. We discuss possible pairing mechanisms in the
context of competing ferromagnetic phases found in this work and the
ferromagnetic spin fluctuations.
