A normally-closed flow rate control valve, comprising: a base block provided with a valve chamber in which a valve seat through which a liquid raw material flows, and a diaphragm that is brought into contact with or separated from the valve seat so as to close/open the valve seat are installed; and a valve opening/closing mechanism that performs opening/closing drive of the diaphragm, wherein the valve opening/closing mechanism includes: a slide bearing part installed on the base block and provided with a bearing; a support post part including a support post that is inserted slidably in the bearing and that moves upward and downward in a diaphragm direction; a piezoelectric actuator part provided between the slide bearing part and the support post part, the piezoelectric actuator part including a piezoelectric element that expands by application of voltage, and presses up the support post part in such a direction as to separate the support post part from the diaphragm with respect to the slide bearing part as a reference; and a valve-actuating part that is provided from the support post part toward the diaphragm and that performs opening/closing drive of the diaphragm along up-and-down movement of the support post part, the support post of the support post part is made of a low thermal expansion member, the slide bearing part includes a bearing lower part that is bottomed and that has an opened upper face, the support post part includes the support post, an upper end support member that is provided on an upper end of the support post and on which an upper end of the piezoelectric actuator part is abutted, and a lower end support member provided between the bearing upper part and the bearing lower part, and an elastic member is installed between the bearing upper part and the lower end support member, characterized in that the slide bearing part further includes a bearing upper part that is screwed movably forward and backward in the bearing lower part and that is provided with the bearing in which the support post is inserted. a base block provided with a valve chamber in which a valve seat through which a liquid raw material flows, and a diaphragm that is brought into contact with or separated from the valve seat so as to close/open the valve seat are installed; and a valve opening/closing mechanism that performs opening/closing drive of the diaphragm, wherein the valve opening/closing mechanism includes: a slide bearing part installed on the base block and provided with a bearing; a support post part including a support post that is inserted slidably in the bearing and that moves upward and downward in a diaphragm direction; a piezoelectric actuator part provided between the slide bearing part and the support post part, the piezoelectric actuator part including a piezoelectric element that expands by application of voltage, and presses up the support post part in such a direction as to separate the support post part from the diaphragm with respect to the slide bearing part as a reference; and a valve-actuating part that is provided from the support post part toward the diaphragm and that performs opening/closing drive of the diaphragm along up-and-down movement of the support post part, the support post of the support post part is made of a low thermal expansion member, the slide bearing part includes a bearing lower part that is bottomed and that has an opened upper face, the support post part includes the support post, an upper end support member that is provided on an upper end of the support post and on which an upper end of the piezoelectric actuator part is abutted, and a lower end support member provided between the bearing upper part and the bearing lower part, and an elastic member is installed between the bearing upper part and the lower end support member, characterized in that the slide bearing part further includes a bearing upper part that is screwed movably forward and backward in the bearing lower part and that is provided with the bearing in which the support post is inserted. a slide bearing part installed on the base block and provided with a bearing; a support post part including a support post that is inserted slidably in the bearing and that moves upward and downward in a diaphragm direction; a piezoelectric actuator part provided between the slide bearing part and the support post part, the piezoelectric actuator part including a piezoelectric element that expands by application of voltage, and presses up the support post part in such a direction as to separate the support post part from the diaphragm with respect to the slide bearing part as a reference; and a valve-actuating part that is provided from the support post part toward the diaphragm and that performs opening/closing drive of the diaphragm along up-and-down movement of the support post part, the support post of the support post part is made of a low thermal expansion member, the slide bearing part includes a bearing lower part that is bottomed and that has an opened upper face, the support post part includes the support post, an upper end support member that is provided on an upper end of the support post and on which an upper end of the piezoelectric actuator part is abutted, and a lower end support member provided between the bearing upper part and the bearing lower part, and an elastic member is installed between the bearing upper part and the lower end support member, characterized in that the slide bearing part further includes a bearing upper part that is screwed movably forward and backward in the bearing lower part and that is provided with the bearing in which the support post is inserted.