A drive mechanism (1) of a camera apparatus includes a worm gear (4) to which a rotational driving force of a drive motor (2) is transmitted, a worm wheel (6) around which a helical gear (5) is formed to engage with the worm gear (4), and a support frame (7) which supports the worm wheel (6) rotatably and movably along a rotation axis. A rotational driving force of the worm gear (4) is transmitted to the worm wheel (6) with reduced gear ratio. An externally threaded portion (10) of a shaft portion (8) of the worm wheel (6) is engaged with an internally threaded portion in a supporting hole (14) of the support frame (7), so that the shaft portion (8) moves along the rotation axis when the worm wheel (6) rotates. Consequently, the rotational driving force transmitted to the worm wheel (6) is converted into a linear thrust force along the rotation axis. This makes it possible to provide a camera apparatus which can develop a larger thrust force and adjust an amount of travel more finely.