And increases the tax burden paid by employees. Yeah - a minimum wage is a form of wealth redistribution. It still ain't a tax, and shouldn't be thought of as one.
Why shouldn't it be thought of as one? The government is (legitimately) coercing an individual or group of individuals to spend more money than they would normally. I hear heads on talk radio refer to all sorts of government coercion as tax, not that I should take my cues from willy-nilly.