A connection module includes a busbar holding module including insulating protectors and an external connection busbar holder disposed above the busbar holding module. The insulating protectors include fixing portions joined to fixed portions provided in the power storage elements or another member to secure the external connection busbar holder. The external connection busbar holder includes a first external connection busbar and a second external connection busbar to which external connection members are bolted and engaging portions that engage with the fixing portions. Each of the fixing portions includes a fixing-reinforcement portion that is displaced to fill the clearance between the fixing portion and the fixed portion in response to engagement with the engaging portion.