We studied the effects of magnetic field strength and sample size on the magnetomechanical response for disk-shaped magnetic elastomers placed on a permanent magnet. The diameter of magnetic elastomer was varied between 14-40 mm, whereas the height was constant at 5 mm. The stress was measured with a unidirectional compression apparatus. It was found that the smallest magnetic elastomer with 14mm diameter did not exhibit magnetomechanical response, on the other hand, clear response was observed for magnetic elastomers with 35mm diameter. This sample size effect was observed at both 310 and 420mT.