The invention relates to a rotating shaft structure and a portable ultrasonic device. The portable ultrasonic device comprises an ultrasonic main machine, a display screen installed on the ultrasonicmain machine and probe modules installed on the ultrasonic main machine, wherein the ultrasonic main machine and the probe modules are rotatably connected by virtue of a first rotating shaft structureand a second rotating shaft structure; the portable ultrasonic device is characterized in that the second rotating shaft structure comprises a rotating shaft lever B and a rotating shaft lever C; therotating shaft lever B comprises a first end and a second end which are opposite; the rotating shaft lever C has a third end and a fourth end which are opposite; the second end is rotatably connectedto the third end, and a limiting component is arranged at the junction of the second end and the third end; the limiting component includes a first limiting part and a second limiting part; the firstlimiting part and the second limiting part cooperate with each other to form one or more limiting position points, so that a rotating shaft B and a rotating shaft C are limited at the limiting position points. The portable ultrasonic device provided by the invention can ensure that a user can observe images on a display while observing a puncture needle and a probe.