  Correlation between instantons and QCD-monopoles is studied in the
abelian-gauge-fixed QCD. From a simple topological consideration, instantons
are expected to appear only around the QCD-monopole trajectory in the
abelian-dominating system. The QCD-monopole in the multi-instanton solution is
studied in the Polyakov-like gauge, where $A_4(x)$ is diagonalized. The world
line of the QCD-monopole is found to be penetrate the center of each instanton.
For the single-instanton solution, the QCD-monopole trajectory becomes a simple
straight line. On the other hand, in the multi-instanton system, the
QCD-monopole trajectory often has complicated topology including a loop or a
folded structure, and is unstable against a small fluctuation of the location
and the size of instantons. We also study the thermal instanton system in the
Polyakov-like gauge. At the high-temperature limit, the monopole trajectory
becomes straight lines in the temporal direction. The topology of the
QCD-monopole trajectory is drastically changed at a high temperature.
