The purpose is to provide a preparation aid for a syringe that can easily push a plunger. The present invention comprises a case accommodating a sealed container containing a first preparation material and a holder having a plunger and holding a syringe containing a second preparation material, wherein the case and the holder relatively and slidably engage with each other to a communication position where the sealed container and the syringe are made to communicate with each other by a needle member in a piercing direction in which the needle member is pierced into the sealed container. Provided is a switching structure comprising a slide engagement part that engages at least one among the holder and the syringe as an engagement target and causes the holder to slide to the communication position, and an operation member having a pushing engagement part that pushes the plunger in the communication position toward the sealed container, wherein the slide engagement part is made to disengage from the engagement target by a pushing force on the operation member between the engagement target and the operation member, and the pushing engagement part and the plunger engage with each other.Le but de la présente invention consiste à fournir une aide à la préparation d'une seringue qui peut pousser facilement un piston. La présente invention comprend un boîtier qui reçoit un récipient scellé contenant un premier matériau de préparation et un support ayant un piston et retenant une seringue contenant un second matériau de préparation, le boîtier et le support venant en prise de manière relative et coulissante l'un par rapport à l'autre vers une position de communication où le récipient scellé et la seringue sont amenés à communiquer l'un avec l'autre par un élément aiguille dans un sens de perforation dans lequel l'élément aiguille perce le récipient scellé. L'invention concerne une structure de commutation qui comporte une partie coulissante de mise en prise qui met en prise l
