The purpose of the present invention is to provide information pertaining to a collapsed state of a blood vessel intended to be punctured, such collapse caused by the pressing of an ultrasonic probe when acquiring ultrasonic images of the blood vessel. A puncture assistance system 10 is provided with: a vascular diameter detecting means 18 for detecting a vascular diameter during acquisition of ultrasonic images from an ultrasonic diagnostic device 11 a puncture assistance information generating means 12 that generates puncture assistance information for determining whether puncturing is possible on the basis of the collapsed state of a blood vessel B due to pressing of an ultrasonic probe 15 against the skin S, such generation performed by comparing a current vascular diameter detected by the vascular diameter detecting means 18 and a pre-stored reference vascular diameter and a monitor 19 for presenting the puncture assistance information. As the puncture assistance information, the following are found: a vascular compression rate representative of the ratio of the vascular diameter during ultrasonic image acquisition relative to the pre-stored reference vascular diameter and a puncture feasibility rate representative of the current ease of puncturing at the blood vessel B due to the pressing of the ultrasonic probe 15.Lobjectif de la présente invention est de fournir des informations relatives à un état rétracté dun vaisseau sanguin destiné à être ponctionné, un tel retrait étant causé par la pression dune sonde ultrasonore lors de lacquisition dimages échographiques du vaisseau sanguin. Un système dassistance de ponction 10 est pourvu de : un moyen de détection de diamètre vasculaire 18 pour détecter un diamètre vasculaire pendant lacquisition dimages échographiques à partir dun dispositif de diagnostic échographique 11 un moyen de génération dinformations dassistance de ponction 12 qui génère des informations dassistance de ponction pour déterminer si une fonc
