Ultrasonic measurements were performed on the cage-structure compound SmBe₁₃. We have investigated the magnetic field-temperature phase diagram of this material by using pulsed magnetic fields. We found that the low-temperature magnetic order is suppressed by a magnetic field of 43 T for H ∥ [001], which is smaller than the estimated value from mean-field approximation assuming the Γ₈ quartet crystal-electric-field ground state and simple antiferromagnetic order. We found that the elastic constant C₄₄ shows softening below the ordering temperature and has a local minimum below 7 T. These facts suggest that the low- temperature state is not a simple antiferromagnetically ordered state. In addition, no elastic anomaly due to rattling modes was found in the present measurements.