An automated analyzer used for chemical analysis, comprising: a control device configured to control each mechanism of the automated analyzer for operations of processes; a container installation portion (2, 2C) in which a container including an openable and closable lid having a protrusion is installed; and a lid opening and closing mechanism portion for opening and closing the lid, wherein the lid opening and closing mechanism portion includes an arm portion including an arm for opening the lid, wherein the arm includes a protrusion contacting portion for contacting the protrusion, and wherein the protrusion contacting portion includes a first surface having an angle greater than 0 degrees and less than 90 degrees when a horizontal surface is set as 0 degrees, characterised in that: the arm extends in the vertical direction with a shaft portion and a lower end portion which has the protrusion contacting portion which protrudes from the shaft portion in a first horizontal direction, the lid opening and closing mechanism portion includes a horizontal driving portion configured to move the arm in said first horizontal direction, the container includes a hinge portion extending in a second horizontal direction, the lid being rotatable about the hinge portion, the protrusion protrudes from a side of the lid in said second horizontal direction such as to move along an arc when the lid rotates about the hinge portion, and the lid opening and closing mechanism portion is configured to open the lid by moving the arm in the first horizontal direction, causing the protrusion to make contact on the protrusion contacting portion, and thus moving the protrusion up in a vertical direction along the shape of the first surface whereby the protrusion reaches the side surface of the shaft portion via the first surface of the arm and the lid reaches an open state exposing an opening of the container for dispensing of a reagent contained in the container, and to close the lid by moving the arm reverse to the first horizontal direction. a control device configured to control each mechanism of the automated analyzer for operations of processes; a container installation portion (2, 2C) in which a container including an openable and closable lid having a protrusion is installed; and a lid opening and closing mechanism portion for opening and closing the lid, wherein the lid opening and closing mechanism portion includes an arm portion including an arm for opening the lid, wherein the arm includes a protrusion contacting portion for contacting the protrusion, and wherein the protrusion contacting portion includes a first surface having an angle greater than 0 degrees and less than 90 degrees when a horizontal surface is set as 0 degrees, characterised in that: the arm extends in the vertical direction with a shaft portion and a lower end portion which has the protrusion contacting portion which protrudes from the shaft portion in a first horizontal direction, the lid opening and closing mechanism portion includes a horizontal driving portion configured to move the arm in said first horizontal direction, the container includes a hinge portion extending in a second horizontal direction, the lid being rotatable about the hinge portion, the protrusion protrudes from a side of the lid in said second horizontal direction such as to move along an arc when the lid rotates about the hinge portion, and the lid opening and closing mechanism portion is configured to open the lid by moving the arm in the first horizontal direction, causing the protrusion to make contact on the protrusion contacting portion, and thus moving the protrusion up in a vertical direction along the shape of the first surface whereby the protrusion reaches the side surface of the shaft portion via the first surface of the arm and the lid reaches an open state exposing an opening of the container for dispensing of a reagent contained in the container, and to close the lid by moving the arm reverse to the first horizontal direction. the arm extends in the vertical direction with a shaft portion and a lower end portion which has the protrusion contacting portion which protrudes from the shaft portion in a first horizontal direction, the lid opening and closing mechanism portion includes a horizontal driving portion configured to move the arm in said first horizontal direction, the container includes a hinge portion extending in a second horizontal direction, the lid being rotatable about the hinge portion, the protrusion protrudes from a side of the lid in said second horizontal direction such as to move along an arc when the lid rotates about the hinge portion, and the lid opening and closing mechanism portion is configured to open the lid by moving the arm in the first horizontal direction, causing the protrusion to make contact on the protrusion contacting portion, and thus moving the protrusion up in a vertical direction along the shape of the first surface whereby the protrusion reaches the side surface of the shaft portion via the first surface of the arm and the lid reaches an open state exposing an opening of the container for dispensing of a reagent contained in the container, and to close the lid by moving the arm reverse to the first horizontal direction.