An image recording apparatus for printing each of a plurality of unit images for each predetermined printing period on an elongated strip-shaped recording medium while transporting said recording medium, said image recording apparatus comprising: a transport part for transporting said recording medium along a transport path; a recording head for ejecting droplets onto said recording medium disposed in a recording region (Rp) on said transport path to print an image on said recording medium; a detector disposed upstream of said recording head and for detecting a thick part of said recording medium, said thick part being thicker than other parts of said recording medium; a relative position switching part for switching the relative position of said recording head and said recording region to a printing position and to a retracted position; a storage part for storing a last start position that is a start position of the last one of said unit images on said recording medium; and a controller for controlling the parts, in response to detection of said thick part by said detector, said controller calculating a remaining job count N indicative of the number of unit images recordable on said recording medium during a time interval between the point of time of the detection and suspension of a printing step and an on-movement transport speed V' indicative of the transport speed of said recording medium at the time of suspension of the printing based on a distance Lo from the detection position of the thick part to an upstream end of said recording region as measured in a transport direction, said printing period T, and a length Lp of said recording region as measured in the transport direction, with said remaining job count N being equal to 0, said controller stopping the printing by means of said recording head promptly, and with said remaining job count N being equal to or more than 1, said controller stopping the printing by means of said recording head after one of said unit images being printed at the time of detection of said thick part by said detector is printed completely to the end and said unit images corresponding to an (N - 1) period are printed completely to the end, said controller stopping the printing by means of said recording head, changing the transport speed of said recording medium by said transport part to said on-movement transport speed V' when the calculated on-movement transport speed V' is different from an on-printing transport speed V that is the transport speed of said printing medium during the printing, keeping the transport speed of said recording medium by said transport part at the on-printing transport speed V when the calculated on-movement transport speed V' is equal to said on-printing transport speed V and switching the relative position of said recording head and said recording region to the retracted position by means of said relative position switching part before said thick part reaches said recording region, said controller switching the relative position of said recording head and said recording region to the printing position by means of said relative position switching part and starting the printing of a new one of said unit images by means of said recording head from a position an integral multiple of said printing period apart from said last start position after said thick part passes through said recording region, said controller updating said last start position stored in said storage part to said start position of a new image period each time the printing of a new unit image starts. a transport part for transporting said recording medium along a transport path; a recording head for ejecting droplets onto said recording medium disposed in a recording region (Rp) on said transport path to print an image on said recording medium; a detector disposed upstream of said recording head and for detecting a thick part of said recording medium, said thick part being thicker than other parts of said recording medium; a relative position switching part for switching the relative position of said recording head and said recording region to a printing position and to a retracted position; a storage part for storing a last start position that is a start position of the last one of said unit images on said recording medium; and a controller for controlling the parts,