  We study the correlation between instantons and QCD-monopoles both in the
lattice gauge theory and in the multi-instanton system using the maximally
abelian gauge. First, we find the existence of an almost linear correlation
between the total length of monopole trajectories and the total number of
pseudoparticles (instantons and anti-instantons) in the $16^{3}\times4$ SU(2)
lattice. Second, we study the features of QCD-monopole in the SU(2)
multi-instanton vacuum on the $16^{4}$ lattice as a random ensemble of
pseudoparticles. A signal of monopole condensation is found as the clustering
of monopole trajectories, when the topological pseudoparticles is sufficiently
dense.
