  In order to extract information about inflationary gravitational waves using
$B$-mode patterns of cosmic microwave polarization anisotropy, we need to
remove the foreground radiation from the Milky Way. In our previous delta-map
method for foreground removal, the number of observation bands was limited to
the number of parameters of the assumed foreground model, and therefore it was
difficult to improve the sensitivity by increasing the number of observation
bands. Here, we extend the previous method so that it can be adapted to an
arbitrary number of observation bands. Using parametric likelihood and
realistic foreground and CMB simulations, we show that our method can increase
the sensitivity to the tensor-to-scalar ratio $r$ without inducing any
significant bias.
