A patch antenna unit and an Antenna in Package (AIP) structure are provided. The patch antenna unit includes: a base substrate; multiple layers of patches stacked on the base substrate, wherein an isolation layer is disposed between adjacent layers of the patches, and configured to generate a radio frequency electromagnetic field, wherein an edge shape of at least one layer in the multiple layers of patches is a continuous and smooth function curve shape, and edge shapes of all sides of a same layer in the multiple layers of patches are a same function curve shape. Impedance bandwidth may be increased while symmetry of the antenna structure is maintained, and requirements of a substrate process are met, thereby increasing operation bandwidth of the AiP structure.