Moving picture encoding method and decoding method

A moving picture decoding method including a prediction mode, in which a motion vector for a target block of decoding is not included in coded bitstreams, and the motion vector for the target block of decoding is created on a decoding side, comprising the steps of:

• in the prediction mode:
• in forward reference frames of candidate blocks including a plurality of adjacent blocks which are located in the same frame as the target block of decoding and adjacent to the target block of decoding,
• in case that there are a plurality of different forward reference frames, determining one forward reference frame from the plurality of reference frames as a forward reference frame used in the prediction mode,
• in case that there is only one forward reference frame, determining the forward reference frame as a forward reference frame used in the prediction mode,
• in case that there is no forward reference frame, determining preset one frame as a forward reference frame used in the prediction mode,
• and thereby determining one forward reference frame as a forward reference frame of the target block of decoding in all of the cases;
• determining a motion vector of the target block of decoding;
• and
• wherein a decoding of a moving picture is performed by using information of the determined reference frame and the determined motion vector;
• and
• wherein in case that there is no adjacent block having a motion vector, a zero vector is set as the determined motion vector.