A sewing apparatus such as a sewing machine includes a cassette mount to which a thread cassette having a thread accommodating section for accommodating a thread supply is detachably attached, at least one detector detecting an operating state of at least one mechanism related with the thread cassette, a determining unit determining whether the thread cassette can be attached to the cassette mount, based on a result of detection by the detector, and an informing unit informing a result of determination by the determining unit.