  The young T Tauri star PDS 70 has two gas accreting planets sharing one large
gap in a pre-transitional disc. Dust continuum emission from PDS 70 c has been
detected by Atacama Large Millimeter/submillimeter Array (ALMA) Band 7,
considered as the evidence of a circumplanetary disc, but the emission from PDS
70 b has not. We constrain the planet mass and the gas accretion rate of the
planets by introducing a model of dust evolution in the CPDs and reproducing
the detection and non-detection. We first develop a 1D steady gas disc model of
the CPDs reflecting the planet properties. We then calculate the radial
distribution of the dust profiles considering the dust evolution in the gas
disc and calculate the total flux density of dust thermal emission from the
CPDs. We find positive correlations between the flux density and three planet
properties, the planet mass, gas accretion rate, and their product called
"MMdot". We then find that the MMdot of PDS 70 c is larger than 0.4 MJ^2/Myr,
and the planet mass and the gas accretion rate are larger than 5MJ and 0.02
MJ/Myr, respectively. This is the first case to succeed in obtaining
constraints on planet properties from the flux density of dust continuum from a
CPD. We also find some loose constraints on the properties of PDS 70 b from the
non-detection. We propose possible scenarios for the planets explaining the
non-detection respectively detection of the dust emission. The first
explanation is that planet c has larger planet mass and/or larger gas accretion
rate than planet b. The other possibility is that the CPD of planet c has a
larger amount of dust supply and/or weaker turbulence than that of planet b. If
the dust supply to planet c is larger than b due to its closeness to the outer
dust ring, it is also quantitatively consistent with that planet c has weaker
H-alpha line emission than planet b considering the dust extinction effect.
