  We study whether or not magnetic monopoles are generated from calorons
defined in the space $\mathbb{R}^3\times S^1$ with the period $\beta$. We give
numerical evidence that one-caloron solution with nontrivial holonomy generates
two loops of magnetic monopole and each loop passing through one of the two
poles of the caloron winds along the time direction for small $\beta$, while
two loops approach each other to fuse into an unwinding loop for large $\beta$,
suggesting the existence of a critical value of $\beta$ separating two
different phases. This work is a first step to explain quark
confinement/deconfinement at finite temperature from the viewpoint of dual
superconductor picture in our framework.
