We know space expanding from the Hubble's law which Edwin Hubble and Milton Humason formulated first in 1929, and nearly 100 years passed, but Flat gravity caused by the expanding universe was covered in a short distance by Newtonian gravity according to inverse square law. It caused gravity anomalies such as the pioneer anomaly that a cause of the blue-shift indicating the slowdown to the sun direction is unclear as planetary probe pioneer 10-11 leaves the sun and the issue of galactic rotation curve which forms flat velocity distribution without rotational speed decreasing in galactic considerable penumbra known as physical unsolved problem. If expanding universe is premised, clause of the expansion that divided recession rate v=H0D in strain constant V0 is added, and Newtonian potential -GM/r(1) premising steady state cosmology be changes to -GM/r(1+v/V0). The clause of this expansion becomes constant　G0=GH0/V0 which distance D and 1/r canceled and total gravitational mass of the universe M0=c3/(2GH0) which can be observed affects specific potential constant which multiplied gravitational mass for the observation and becomes -(G/r+G0)M. Flat gravity based on Hubble's law added to Newtonian gravity accords with the value of the gravity anomaly without assuming dark matter.