  We investigate production of primordial black holes from first-order
electroweak phase transition in the framework of the nearly aligned Higgs
effective field theory, in which non-decoupling quantum effects are properly
described. Since the mass of such primordial black holes is evaluated to be
about $10^{-5}$ of the solar mass, current and future microlensing observations
such as Subaru HSC, OGLE, PRIME and Roman Space Telescope may be able to probe
the electroweak phase transition. We study parameter regions where primordial
black holes can be produced by the first-order electroweak phase transition,
and explore their detectability at these observations. Complementarity of
primordial black hole observations, gravitational wave observations and
collider experiments is also discussed for testing the nature of the
electroweak phase transition.
