How does the public assess an appropriate financial allocation to science promotion? This article empirically examined the subadditivity effect in the judgment of budgetary allocation. Results of the first experiment showed that the ratio of the national budget allocated for science promotion by participants increased when science was decomposed into more specific categories compared to when it was presented as "science promotion" alone. Consistent with these findings, results of the second experiment showed that the allotment ratio to science promotion decreased when the number of other expenditure items increased. Meanwhile, the third experiment revealed that in the case of a budgetary cutback, the total amount taken from science promotion greatly increased when science was decomposed into subcategories. The subadditivity effect and increase in the total allotment ratio by unpacking science promotion was confirmed by these three experiments not only on budgetary allocation but also on budgetary cutback.