Evaporation E from Lake Kasumigaura, the second largest lake in Japan, was estimated continuously at a 3-h interval for the period of 2008–2012 by means of a bulk formulation applied to 23,468 grids covering the whole lake surface. A functional form of the bulk coefficient was determined from eddy correlation measurements at the central part of the lake. Wind speed (U), temperature, humidity, and infrared radiation surface temperature, from which the specific humidity q_s of the water surface was determined, were also measured. Specific humidity q and U at 10 m above the surface of each grid were derived from routine measurements at meteorological stations in and around the lake, by applying the Kriging interpolation scheme. This operation produced not only the totals but also the horizontal variation in E. The mean annual E was estimated as 911 (± 42) mm, which is within the range of previous estimates of 671–1003 mm/yr. Seasonally, E followed the change in net radiation with a short (< 1 month) phase delay caused by stored energy in the water body. Year-to-year variation was small. Horizontally E tended to be larger in the central and southern parts of the lake, reflecting stronger wind regime there.