  We study two-leg Heisenberg ladder with four-spin cyclic interaction using
the (dynamical) density-matrix renormalization group method. We demonstrate the
dependence of the low-lying excitations in the spin wave, staggered dimer
order, and scalar-chirality order structure factors on the four-spin cyclic
interaction. We find that the cyclic interaction enhances spin-spin
correlations with wave vector around momentum $(q_x,q_y)=(\frac{\pi}{2},0)$.
Also, the presence of long-range order in the staggered dimer and
scalar-chirality phases is confirmed by a $\delta$-function peak contribution
of the structure factors at energy $\omega=0$.
