An electronic device including a detection sensor is disclosed. The electronic device may include: a housing structure including a first housing and a second housing movably coupled to the first housing in a moving direction, a flexible display supported by the first housing and the second housing, and having a size of a display area visible at a front surface of the housing structure configured to change based on relative movement by the second housing with respect to the first housing, a detection sensor including a first electrode and a second electrode disposed side by side, and a dielectric disposed between the first electrode and the second electrode, and configured to detect a change in the size of the display area, and a processor.