  The evolution of the magnetic field and angular momentum in the collapsing
cloud core is studied using three-dimensional resistive MHD nested grid
simulations. Starting with a Bonnor-Ebert isothermal cloud rotating in a
uniform magnetic field, we calculate the cloud evolution from the molecular
cloud core (n=10^4 cm^-3) to the stellar core (n \simeq 10^22 cm^-3). The
magnetic field strengths at the center of the clouds converge to a certain
value as the clouds collapse, when the clouds have the same angular momenta but
different strengths of the magnetic fields at the initial state. For 10^12
cm^-3 < n < 10^16 cm^-3, Ohmic dissipation considerably removes the magnetic
field from the collapsing cloud core, and the magnetic field lines, which are
strongly twisted for n <10^12 cm^-3, is de-collimated. The magnetic field lines
are twisted and amplified again for nc > 10^16 cm^-3, because the magnetic
field is recoupled with the warm gas. Finally, protostars at their formation
epoch have 0.1-1kG of the magnetic fields, which are comparable to
observations. The magnetic field strength of protostar slightly depends on the
angular momentum of the host cloud. The protostar formed from the slowly
rotating cloud core has a stronger magnetic field. The evolution of the angular
momentum is closely related to the evolution of the magnetic field. The angular
momentum in the collapsing cloud is removed by the magnetic effect. The formed
protostars have 0.1-2 days of the rotation period at their formation epoch,
which are slightly shorter than the observation. This indicates that the
further removal mechanism of the angular momentum such as interaction between
the protostar and disk, wind gas or jet is important in further evolution of
the protostar.
