A diagnosis device of a capacitor discharge ignition device for an engine that detects, as a singularity, a leading edge or a trailing edge of a voltage between output terminals of an ignition power supply portion that generates a voltage for charging an ignition capacitor, counts the number of singularities detected while a crankshaft rotates through a measurement section, which is a section of a certain crank angle determined with reference to a pulse signal obtained by a signal generator that generates a pulse signal at a specific crank angle position of an engine, and diagnoses an abnormality of the ignition device and a cause of the abnormality by comparing the count value of singularity with the number of times of normal ignition of the engine performed while the crankshaft rotates through the measurement section.