  XRPIX is the monolithic X-ray SOI (silicon-on-insulator) pixel detector,
which has a time resolution better than 10 $\rm{\mu}$s as well as a high
detection efficiency for X-rays above 10 keV. XRPIX is planned to be installed
on future X-ray satellites. To mount on satellites, it is essential that the
ADC (analog-to-digital converter) be implemented on the detector because such
peripheral circuits must be as compact as possible to achieve a large imaging
area in the limited space in satellites. Thus, we developed a new XRPIX device
with the on-chip ADC, and evaluated its performances. As the results, the
integral non-linearity was evaluated to be 6 LSB (least significant bit),
equivalent to 36 eV. The differential non-linearity was less than 0.7 LSB, and
input noise from the on-chip ADC was 5~$\rm{e^{-}}$. Also, we evaluated
end-to-end performance including the sensor part as well as the on-chip ADC. As
the results, energy resolution at 5.9 keV was 294 $\rm{\pm}$ 4 eV in full-width
at half maximum for the best pixel.
