Samādhi sūtras is the categorical name referring to sūtras which are titled with the name of a Mahāyāna samādhi. Each sūtra is supposed to explain a meditative technique that generates an altered mental state. In fact, however, many Samādhi sūtras do not have any description of such a state. In this paper, we take up the Śūraṃgama-samādhi Sūtra (Śgs) and conclude that it also has no description of a technique and its samādhi does not involve meditative practice. On the other hand, the entire sūtra is dedicated to expounding the mystical powers of the Sūraṃgama-samādhi. Thus, the samādhi in the Śgs consists only of this power aspect. Focusing on this, we can find an interesting example that sentient beings raise the intention to achieve enlightenment after seeing the samādhi’s power. This example indicates that the Śgs tries to evoke faith in the Mahāyāna by means of showing the power of a Mahāyāna samādhi. Finally, I argue that the purpose of the composition of the Śgs is not as a meditative manual but in order to encourage sentient beings toward the Mahāyāna.