A single terahertz wave time-waveform measuring device 1 acquires information on an object to be measured 9 by using a terahertz wave, and includes a light source 11, a beam diameter adjuster 12, a separator 13, a terahertz wave generator 21, a light path length difference adjuster 31, a pulse front tilting unit 32, a polarizer 33, a wave synthesizer 41, an electro-optic crystal 42, an analyzer 43, and a photodetector 44. The terahertz wave generator 21 generates a pulse terahertz wave in response to an input of pump light and outputs the pulse terahertz wave. The pulse front tilting unit 32 makes pulse fronts of the terahertz wave and the probe light when being input into the electro-optic crystal 42 nonparallel to each other by tilting the pulse front of the probe light.