Network analysis is between WBS and Gantt Chart:
Managing Information Technology Projects ¹ discusses Network Analysis in the second chapter: The Foundations of Project Management, just after the WBS and before the Gantt Chart.
The same is true for Project Management: A Systems Approach to Planning, Scheduling, and Controlling ², where WBS is discussed in chapter 11: Planning, Network scheduling - in chapter 12, and Gantt Chart in chapter 13: Project Graphics.
In fact, in practice, the activity network is planned just after planning the WBS. It can hardly be done before, since it requires the elements which figure in WBS, and is required to do Gantt Chart with is based on the network analysis itself.
Project-wise, it is at the same stage as the WBS.
On the diagram from your question, if WBS is Define/Decompose stage, Gantt Chart would be at the very end (Develop schedule), and network analysis - somewhere behind the two, probably after estimating resources (in order to get a good idea of possible paths).
¹ Managing information technology projects: applying project management strategies to software, hardware, and integration initiatives by James Taylor, 2004, ISBN 0814408117
² Project Management: A Systems Approach to Planning, Scheduling, and Controlling by Harold Kerzner, 8th Ed., 2003, ISBN 0471225770