  In recent letter [Phys.~Rev.~Lett {\bf 123}, 110602 (2019)], Y.~Hasegawa and
T.~V.~Vu derived a thermodynamic uncertainty relation. But the bound of their
relation is loose. In this comment, through minor changes, an improved bound is
obtained. This improved bound is the same as the one obtained in
[Phys.~Rev.~Lett {\bf 123}, 090604 (2019)] by A.~M.~Timpanaro {\it et. al.},
but the derivation here is straightforward.
