In order to solve at least one of the drawbacks that result from a state in which a plurality of secondary batteries are integrated, a battery apparatus having a plurality of flat secondary batteries 70 includes housing 1 with opening 30, and lid 31 capable of opening and closing opening 30 of housing 1, wherein the plurality of secondary batteries 70 are disposed in a vertical orientation in parallel with each other in housing 1 and are capable of being singly inserted into and taken out of housing 1 through opening 30.