Provided is an image diagnostic device with which the start and end of the in-flow of a contrast medium are automatically assessed. An image diagnostic device assesses the start and end times of the in-flow of a contrast medium into organs in a lifeform which is a subject. The image diagnostic device comprises: an input unit (11) which receives an input of a signal from a contrast medium which is acquired from such as an image acquisition unit (22) a luminosity evaluation unit (13) which creates a luminosity curve that denotes a change over time in signal strength a function evaluation unit (14) which approximates the luminosity curve with an S-shaped function and creates a model function an assessment unit (12), further comprising a circulation evaluation unit (15) which uses a tangent line at an inflection point of the model function and assesses the start and end of the in-flow of the contrast medium and a display unit (19) which displays the result which is evaluated with the assessment unit (12). The present invention allows automatically assessing the start and end times of the in-flow of the contrast medium.
