The utility model relates to a roller-type tobacco stem continuous microwave expanding device, which comprises a microwave source cavity (2) which is installed on a rack (1), a material conveying roller (6) which transversely penetrates through the middle of the microwave source cavity and can rotate along an axis, a roller driving mechanism (23) and an air cooling system (26) which is arranged on a protective cover. Fixed microwave suppressing members (5 and 5') are sheathed at the two ends of the microwave source cavity outside the material conveying roller. The feeding end and the discharging end of the material conveying roller are respectively connected with a fixed feeding end roller (3) and a discharging end roller (10) through revolving members. The feeding end roller is connected with a feeding device (7). The lower part of the discharging end roller is connected with a discharging device (12). The upper part of the discharging end roller is connected with a dust catcher (9). The protective cover (24) covers the microwave source cavity and the microwave suppressing members. The roller-type tobacco stem continuous microwave expanding device can be used for preparing highly-expanded low-crushing-rate tobacco stems to further obtain high-quality cut stems and can satisfy the requirements of specialized, large-scale and continuous production.