Patent attributes
Provided are a connecting structure and a hydraulic drive device capable of simply and reliably connecting two shaft bodies together while appropriately preventing rotation and runout therebetween. The connecting structure includes a first shaft body and a second shaft body connected to each other at respective end portions and provided so as to be rotatable integrally with each other about a rotation axis. An anti-runout support portion of the first shaft body and that of the second shaft body are engaged with each other so as to restrict relative movement between the first and second shaft bodies with respect to a radial direction. An anti-rotation support portion of the first shaft body and that of the second shaft body are engaged with each other so as to restrict relative movement between the first and second shaft bodies with respect to a rotation direction about the rotation axis.