High-voltage transmission electron microscopes (HVTEMs), which can visualize internal structures of micron thick samples, intrinsically have large instrument sizes because of the static voltage isolation. In this Letter, we develop a compact HVTEM, employing a linear accelerator, a subpicosecond beam chopper, and a linear decelerator. 100 kV electrons initially accelerated by a static field are accelerated at radio frequency (rf) up to 500 kV, transmitting through the sample and finally rf decelerated down to 200 kV to be imaged through a 200 kV energy filter. 500 kV imaging, as well as subnanometer resolution at 200 kV, have been demonstrated.