An autofocus adjustment method for a three-dimensional imaging device, includes: a step of, when a first lens position is not found during search operation of a first focus lens of a first imaging optical system within a first search range, allowing a second focus lens of a second imaging optical system to perform search operation within the first search range, and during the search operation, searching for a second lens position at which the second focus lens focuses on the subject based on a second viewpoint image from the second imaging unit; a step of allowing the second focus lens to move to the second lens position; a step of calculating the first lens position based on the second lens position and a focus position displacement amount preliminarily stored in a storage; and a step of allowing the first focus lens to move to the first lens position thus calculated.