The training data generation apparatus (10) includes an acquisition unit (12), a marker detection unit (14), a label generation unit (16), and an output unit (18). The acquisition unit (12) acquires a radar image based on scattered signal from an object. The marker detection unit (14) acquires a supplementary image of a region including the object captured in sync with a detection of the scattered signal, detects a marker in the supplementary image, and extracts an identifier of the marker. The label generation unit (16) generates a label using the extracted identifier. The output unit (18) outputs an output data in which the radar image and the generated label are associated with each other.