  We investigate a possibility of primordial black hole (PBH) formation with a
hierarchical mass spectrum in multiple phases of inflation. As an example, we
find that one can simultaneously realize a mass spectrum which has recently
attracted a lot of attention: stellar-mass PBHs ($\sim\mathcal{O}(10)M_\odot$)
as a possible source of binary black holes detected by LIGO/Virgo
collaboration, asteroid-mass ($\sim\mathcal{O}(10^{-12})M_\odot$) as a main
component of dark matter, and earth-mass ($\sim\mathcal{O}(10^{-5})M_\odot$) as
a source of ultrashort-timescale events in Optical Gravitational Lensing
Experiment microlensing data. The recent refined de Sitter swampland conjecture
may support such a multi-phase inflationary scenario with hierarchical mass
PBHs as a transition signal of each inflationary phase.
