An objective measurement method for office productivity has been proposed. Firstly, office productivity and related matters have been defined. A field survey in a business office has been conducted, and composition and weight of elemental abilities for office work have been derived for each occupation. Then, a task performance test system to evaluate office productivity, CPTOP, has been developed. And the more, an experimental evaluation of the implementation of CPTOP has been carried out, and appropriateness for standard test has been checked. Furthermore, another experiment has confirmed that CPTOP reflects changes of indoor environment.