The present invention relates to a battery compartment capable of selectively accommodating an integrated battery unit and a plurality of cylindrical batteries. This battery compartment comprises a housing adapted to fit the integrated battery unit and a support member which is pivotably placed about a support portion provided to a side interior wall of the housing between a supporting position substantially perpendicular to the side interior wall to laterally support the plurality of cylindrical batteries and a recessed position along the side interior wall to be recessed from an accommodating space for the integrated battery unit. This support member is always urged toward the supporting position and a loading of the integrated battery unit is carried out in such a manner that the support member is displaced to the recessed position against a resilience of the support member toward the supporting position.