Flexible display device having a multi-thickness function layer

A flexible display device comprising:

• a flexible display panel comprising:
• a display substrate including:
• an active area;
• and
• a non-active area extending outside the active area and including a pad area and a bending area to be folded between the active area and the pad area;
• a thin film encapsulation layer on a first surface of the display substrate;
• a driving portion;
• and
• a function layer below a second surface opposite to the first surface of the display substrate,
• wherein the function layer includes a step portion having a first thickness and a second thickness greater than the first thickness, and
• wherein a curvature of the bending area corresponds to the first thickness of the function layer.