Radiatively inefficient accretion flows (RIAFs) are a common feature of low-luminosity accretion flows, including quiescent states of X-ray binaries and low-lunimosity active galactic nuclei. Thermally driven winds are expected from such hot accretion flows. By assuming that the flow has a self-similarity structure in the radial direction, we solved the vertical structure of the wind and accretion flows simultaneously and evaluated the mass loss rates by wind. We have found that the ratio of the outflow rate to the accretion rate is approximately unity for a viscosity parameter of alpha less than or similar to 0.1, despite some uncertainties in the angular momentum and temperature distributions. That is, the accretion rate in the RIAFs is roughly proportional to the radius. Moreover, we elucidated the effect of cooling by wind on the underneath accretion flow, finding that this effect could be important for calculating the energy spectrum of the RIAF Observational implications are briefly discussed in the context of Sgr A*.