This study demonstrated the anomalous swelling behavior of graded rubber in toluene at 25°C. Ethylene-propylene rubber with a graded crosslink density in the thickness direction was prepared using a compression molding machine, under a temperature gradient (upper temperature: 200°C, lower temperature: 150°C). The crosslink densities of each surface of graded rubber corresponded to those of the homogeneous samples, which were 3.39 × 10⁻⁶ mol/cm³ and 3.74 × 10⁻⁷ mol/cm³ for samples crosslinked at 200°C and 150°C, respectively. The swelling behavior of graded rubber occurred in two distinct states: (1) after 20 min (short period), the rubber bent concavely toward the low-crosslink side, and (2) after 540 min (long period), it bent toward the high-crosslink side. According to Flory–Rehner's theory, the low-crosslink side is expected to be on the outer side. However, in the state (1), the high-crosslink side became the outer side. The possible mechanism can be explained by the theory of gel under constrained swelling. The unswollen region restricts in-plane expansion of the low-crosslink region, causing inhomogeneous stress that bent graded rubber toward the low-crosslink side in state (1). These findings introduce a novel method for developing soft robotic actuators and self-shaping materials.