Of all the factors leading to overwork can be classified into two groups——historical factors and institutional factors. While the former refers to the overwork that people, restricted by historical conditions, have to undertake to obtain basic life materials with low labor productivity, the latter refers to the overwork resulting from institutional arrangements. To analyze the causes leading to the overwork, historical factors have been playing the basic role, and only for the past decades, its impacts have been getting smaller and smaller in some developed countries. Institutional factors, in comparison, are the main causes, in particular when the work is done collectively. As a result, it can only be effective to eliminate the overwork by changing institutional factors. Making changes on historical factors, on the contrary, is both unnecessary and ineffective.