An object of an embodiment of the present invention is to provide a method
with which it is possible to easily distinguish a proliferation phase of
a cell cycle from a resting phase thereof in real time. The object of the
embodiment of the present invention is attained by providing a method for
performing phase identification of the cell cycle, the method including:
visualizing one or more gene-expression products as markers whose amounts
in a cell change in a cell-cycle dependent manner; and detecting the
products so as to distinguish the proliferation phase of the cell cycle
from the resting phase thereof.