Abstract: An agricultural assistance system includes: an operation mechanism that contacts a plant to perform a predetermined operation; and a control unit. The control unit includes: a model generation unit that generates a three-dimensional model of a plant based on a combination of predetermined generation conditions; a training unit that generates a first trained model trained with training data, the training data including: a value of a predetermined parameter in the three-dimensional model; and an image of a plant; an image obtainment unit that obtains an image of a target plant to be evaluated; a model obtainment unit that obtains the first trained model; a parameter estimation unit that estimates, based on the first trained model and the image of the target plant to be evaluated, a value of the predetermined parameter for a predetermined site in the target plant to be evaluated; and an operation instruction unit.