In order to obtain an index which generally shows the work burden extent of various works carried out in an automobile assembling factory or the like, for each work content, the maximum muscle contraction ratio is measured after the work has been continued for 5 seconds, the work burden index (L) is calculated from the measured ratio value, and the equivalent work burden in a standard work is calculated from the calculated work burden index (L) for 5 seconds. The work burden index (TVAL) of actual work is calculated from the equivalent work burden and the actual work time. Suitably, a work routine plan is corrected such that the obtained TVAL is normalized with an apparatus comprising means for storing the equivalent work burden for each work content, means for displaying an image of the work content, and means for inputting work content parameter and so forth while watching the displayed image.