  We explore the potential use of the Radio Continuum (RC) survey conducted by
the Square Kilometre Array (SKA) to remove (delens) the lensing-induced B-mode
polarization and thus enhance future cosmic microwave background (CMB) searches
for inflationary gravitational waves. Measurements of large-scale B-modes of
the CMB are considered to be the best method for probing gravitational waves
from the cosmic inflation. Future CMB experiments will, however, suffer from
contamination by non-primordial B-modes, one source of which is the lensing
B-modes. Delensing, therefore, will be required for further improvement of the
detection sensitivity for gravitational waves. Analyzing the use of the
two-dimensional map of galaxy distribution provided by the SKA RC survey as a
lensing mass tracer, we find that joint delensing using near future CMB
experiments and the SKA phase 1 will improve the constraints on the
tensor-to-scalar ratio by more than a factor of $\sim 2$ compared to those
without the delensing analysis. Compared to the use of CMB data alone, the
inclusion of the SKA phase 1 data will increase the significance of the
constraints on the tensor-to-scalar ratio by a factor $1.2$-$1.6$. For LiteBIRD
combined with a ground-based experiment such as Simons Array and Advanced ACT,
the constraint on the tensor-to-scalar ratio when adding SKA phase 2 data is
improved by a factor of $2.3$-$2.7$, whereas delensing with CMB data alone
improves the constraints by only a factor $1.3$-$1.7$. We conclude that the use
of SKA data is a promising method for delensing upcoming CMB experiments such
as LiteBIRD.
