<p>The belief in supernatural punishment is suggested to play a role in sustaining group cooperation. We propose the concept of artificial supernatural punishment (ASP) to examine the stability of and changes in beliefs and cooperation within an experimental framework: each participant decides the extent to which they wish to cooperate in a public goods game, after which some participants experience a random reduction of points. A total of 179 participants registered with a crowdsourcing service were assigned to either a random instruction condition or an ASP instruction condition, wherein the reduction targets were explained as either random or proportional to participants’ cooperation levels. That is, in the latter case, less cooperative participants were more likely to be chosen as targets, leading participants to anticipate a link between low cooperation and reductions, even though the selection was random. As a baseline, 93 additional participants played only the public goods game. The ASP instruction facilitated cooperation in the first game round compared with the random instruction condition; however, this effect was not sustained and overall cooperation levels did not significantly differ from other conditions. Approaches to mitigate the instability of cooperation dependent on beliefs in supernatural punishment are discussed.</p>