A recording medium drive apparatus including a detecting device for detecting the presence of recording media in a housing section of the apparatus. The detecting device including a pivoting member having a detecting end which is biased to slide along a side face of a recording medium as the recording medium is transferred to/from the housing section. An auxiliary member is provided to prevent the detecting end from entering a groove formed in the side face of the recording medium, thereby preventing incorrect detection that the recording medium is removed from the housing section. The auxiliary member includes a spring leaf which slides along the side face above or below the groove, and a supporting projection, mounted on the detecting end, is supported by an inner face of the leaf spring, thereby preventing the detecting end from moving more than a short distance into the groove. Thus, a position of the detecting member does not change as over the entire length of the side face of the recording medium, so that a constant detection output can be maintained. Consequently, it is possible to reliably detect the ends of the recording medium as it is transferred into and out of the housing section.