While the pitchers of most blenders are usually machine washable, the bases, with their electrical parts aren’t. The best way to clean them is with a cloth and hot soapy water. Do so after each use so that food doesn’t get stuck on it.
Just remember to always unplug your appliance before you start cleaning it. While all of the electrical components are covered, you don’t want to take any chances and be accidentally electrocuted. Never submerge your juicer base in water.