Thermoacoustic oscillation is a harmful vibration in combustors of a gas turbine engine because it can damage the combustors. Development of a suppression method of thermoacoustic oscillation is urgent necessity. Recently, a coupling-induced amplitude death phenomenon was reported experimentally and numerically in thermoacoustic oscillators of Sondhauss type. Since the coupling was established only by using hollow tubes that connects two oscillators, this method can be a simple and reliable method to stop the oscillations, compared to active control method involving electronics and acoustic drivers. In this study, the tube coupling is further tested for the coupled thermoacoustic oscillators with frequency detuning, in order to explore the possibility of stronger suppression effect. The linear stability of the coupled oscillators is numerically obtained based on hydrodynamic equations. We describe that the amplitude death is realized with much smaller tube diameter than that of coupled thermoacoustic oscillators with no detuning. Also, we describe that the tube length resulting in the amplitude death is different from that of coupled identical oscillators. These numerical results are compared with experiments to confirm the validity.