  We examine the dust-to-gas ratio as a function of metallicity for dwarf
galaxies [dwarf irregular galaxies (dIrrs) and blue compact dwarf galaxies
(BCDGs)]. Using a one-zone model and adopting the instantaneous recycling
approximation, we prepare a set of basic equations which describes processes of
dust formation and destruction in a galaxy. Four terms are included for the
processes: dust formation from heavy elements ejected by stellar mass loss,
dust destruction in supernova remnants, dust destruction in star-forming
regions, and accretion of heavy elements onto preexisting dust grains. Solving
the equations, we compare the result with observational data of nearby dIrrs
and BCDGs. The solution is consistent with the data within the reasonable
ranges of model parameters constrained by the previous examinations. This means
that the model is successful in understanding the dust amount of nearby
galaxies. We also show that the accretion rate of heavy element onto
preexisting dust grains is less effective than the condensation of heavy
elements in dwarf galaxies.
